user5850: Sometimes during meditation (Vipassana), I've noticed how the mind tends to get back to breathing by itself, without effort. Can I consider this a progress in meditation? I know that it would be a hindrance to like this when it happens or to dislike when it doesn't happen. 
The question is: does this say something about the mind? (I've been practicing daily for the last 9 months).

user-1: A way to measure ones overall progress in the practice, is to see if the root defilements of "Greed, Hatred and Delusion" are either increased or decreased. 

user295: There are multiple measures of progress:

Fulfilling the 3 trainings: progress on this can be asses from the stage in (Ekā,dasaka) Cetanā’karaṇīya Sutta and related suttas
How diligent (appamāda,vihārī) you are in spiritual development - Pamāda Vihārī Sutta
Development of the 7 factors of enlightenment and the Bodhipakkhiyādhammā out of this I would emphasize awareness and equanimity but there is a lot of overlap with other measures 
Level of purification of mind as in Ratha,vinīta Sutta
Overcoming latent tendencies and unwholesome roots Pahāna Sutta, Avijja Pahana Sutta 2, (Akusala,mūla) Añña,titthiya Sutta
Abandoning hindrances - Nīvarana,pahana Vagga
Jhana route to Nirodha
Loosing of fetters and stages of sainthood
etc.

I deemphasize the last two in the list above for average or novice meditators.

Sometimes during meditation (Vipassana), I've noticed how the mind tends to get back to breathing by itself, without effort. Can I consider this a progress in meditation? I know that it would be a hindrance to like this when it happens or to dislike when it doesn't happen.

If you take the Five hindrances one is uddhacca-kukkucca. Uddhacca is restlessness or actively wondering mind. Staying with one object is  abandoning uddhacca-kukkucca. Also it can be viewed as development of concentration which is a factor in many of these measures above.
Also keep in mind when you regularly think or try to measure your progress you regress in your meditation. You should do this very irregularly perhaps one or so in a few months otherwise this will itself lead to uddhacca-kukkucca.

The question is: does this say something about the mind? 

You are developing concentration and coming out of restless worry hence some level of purification of the mind is happening.

user715: Returning to the object of noting sounds like Khanika Samadhi

Pure Vipassana yogis can appreciate and understand the power of Khanika concentration. For when their noting gains momentum, they can see for themselves how the noting goes on by itself uninterruptedly without a break. The noting seems to run on its own steam without any need for the yogi to make any concerted or deliberate effort. Thus, it is not unusual for a yogi to be able to sit for an hour, and even several hours, absorbed in noting. During good noting, especially at the insight knowledge of equanimity (sankhara-upekkhañana), the mind just stays put on its objects and refuses to wander. Even if one wants to send the mind out, it refuses to go and it recoils back to whatever Vipassana object it is noting. There have been cases of yogis being able to sit for six or seven hours in a stretch, or even longer. From this, one can deduce that there must be strength in Khanika concentration; otherwise how would yogis be able to sit in rapt concentration for such lengths of time.

http://www.angelfire.com/indie/anna_jones1/vip-jhana.html

5850: <p>Sometimes during meditation (Vipassana), I've noticed how the mind tends to get back to breathing by itself, without effort. Can I consider this a progress in meditation? I know that it would be a hindrance to like this when it happens or to dislike when it doesn't happen. </p>

<p>The question is: does this say something about the mind? (I've been practicing daily for the last 9 months).</p>
 -1: <p>A way to measure ones overall progress in the practice, is to see if the root defilements of <em>"Greed, Hatred and Delusion"</em> are either increased or decreased. </p>
 295: <p>There are multiple measures of progress:</p>

<ul>
<li>Fulfilling the <a href="https://en.wikipedia.org/wiki/Threefold_Training" rel="nofollow noreferrer">3 trainings</a>: progress on this can be asses from the stage in <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2010/02/33.3b-Ekadasaka-Cetanakaraniya-a11.2-piya.pdf" rel="nofollow noreferrer">(Ekā,dasaka) Cetanā’karaṇīya Sutta</a> and related suttas</li>
<li>How diligent (appamāda,vihārī) you are in spiritual development - <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2013/04/47.6-Pamada-Vihari-S-s35.97-piya.pdf" rel="nofollow noreferrer">Pamāda Vihārī Sutta</a></li>
<li>Development of the <a href="https://en.wikipedia.org/wiki/Seven_Factors_of_Enlightenment" rel="nofollow noreferrer">7 factors of enlightenment</a> and the <a href="https://en.wikipedia.org/wiki/Bodhipakkhiy%C4%81dhamm%C4%81" rel="nofollow noreferrer">Bodhipakkhiyādhammā</a> out of this I would emphasize awareness and equanimity but there is a lot of overlap with other measures </li>
<li>Level of purification of mind as in <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2009/12/28.3-Rathavinita-S-m24-piya.pdf" rel="nofollow noreferrer">Ratha,vinīta Sutta</a></li>
<li>Overcoming latent tendencies and unwholesome roots <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2010/02/31.1-Pahana-S-s36.3-piya.pdf" rel="nofollow noreferrer">Pahāna Sutta</a>, <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2009/12/16.9-Avijja-Pahana-S-2-s35.80-piya.pdf" rel="nofollow noreferrer">Avijja Pahana Sutta 2</a>, <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2009/12/16.4-Akusalamula-Annatitthiya-S-a-3.68-piya.pdf" rel="nofollow noreferrer">(Akusala,mūla) Añña,titthiya Sutta</a></li>
<li>Abandoning hindrances - <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2009/12/16.3-Nivarana-Pahana-Vagga-a1.2-piya.pdf" rel="nofollow noreferrer">Nīvarana,pahana Vagga</a></li>
<li>Jhana route to Nirodha</li>
<li>Loosing of fetters and stages of sainthood</li>
<li>etc.</li>
</ul>

<p>I deemphasize the last two in the list above for average or novice meditators.</p>

<blockquote>
  <p>Sometimes during meditation (Vipassana), I've noticed how the mind tends to get back to breathing by itself, without effort. Can I consider this a progress in meditation? I know that it would be a hindrance to like this when it happens or to dislike when it doesn't happen.</p>
</blockquote>

<p>If you take the <a href="https://en.wikipedia.org/wiki/Five_hindrances" rel="nofollow noreferrer">Five hindrances</a> one is <a href="https://en.wikipedia.org/wiki/Auddhatya" rel="nofollow noreferrer">uddhacca</a>-<a href="https://en.wikipedia.org/wiki/Kaukritya" rel="nofollow noreferrer">kukkucca</a>. Uddhacca is restlessness or actively wondering mind. Staying with one object is  abandoning <a href="https://en.wikipedia.org/wiki/Auddhatya" rel="nofollow noreferrer">uddhacca</a>-<a href="https://en.wikipedia.org/wiki/Kaukritya" rel="nofollow noreferrer">kukkucca</a>. Also it can be viewed as development of concentration which is a factor in many of these measures above.</p>

<p>Also keep in mind when you regularly think or try to measure your progress you regress in your meditation. You should do this very irregularly perhaps one or so in a few months otherwise this will itself lead to <a href="https://en.wikipedia.org/wiki/Auddhatya" rel="nofollow noreferrer">uddhacca</a>-<a href="https://en.wikipedia.org/wiki/Kaukritya" rel="nofollow noreferrer">kukkucca</a>.</p>

<blockquote>
  <p>The question is: does this say something about the mind? </p>
</blockquote>

<p>You are developing concentration and coming out of restless worry hence some level of purification of the mind is happening.</p>
 715: <p>Returning to the object of noting sounds like Khanika Samadhi</p>

<blockquote>
  <p>Pure Vipassana yogis can appreciate and understand the power of Khanika concentration. For when their noting gains momentum, they can see for themselves how the noting goes on by itself uninterruptedly without a break. The noting seems to run on its own steam without any need for the yogi to make any concerted or deliberate effort. Thus, it is not unusual for a yogi to be able to sit for an hour, and even several hours, absorbed in noting. During good noting, especially at the insight knowledge of equanimity (sankhara-upekkhañana), the mind just stays put on its objects and refuses to wander. Even if one wants to send the mind out, it refuses to go and it recoils back to whatever Vipassana object it is noting. There have been cases of yogis being able to sit for six or seven hours in a stretch, or even longer. From this, one can deduce that there must be strength in Khanika concentration; otherwise how would yogis be able to sit in rapt concentration for such lengths of time.</p>
</blockquote>

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