Q:

Bike recommendation for daily commute

I am a 6ft, 172 pound being. Just moved to boston and now that the weather is better, I am looking for a bike which I can use for my daily office commute (around 3ish mile one way). I am willing to spend around 350-500$. Rather than relying on some random bike store's recommendation, I would ask here.
Open to all recommendations, road/hybrid bikes, fixie/geared, etc. Am a casual biker, but am capable of assembling/servicing the bike if need be. 
Road conditions: apart from the cracks and some rough roads of boston, should to good. No off-roading with this bike.
Goods: Will have a backpack, laptop and some minor stuff.
Purpose: Commuting and pleasure riding on weekends, nothing competitive.
Folding bike: Don't see any use of it.

A:

Given the added details in the question, I'd probably agree with @tommy_o's answer and @armb's comment, but would also say this:
It sounds like you do not currently ride and are looking to start. If this is the case, I wouldn't be tempted to spend too much money first time around. 
Obviously you need to spend enough to be comfortable that what you buy is not going to fall apart. But beyond that, your scenario will probably go one of three ways.

You'll end up using the bike just for commuting. In which case 30 miles a week is not heavy use and you don't need any kind of special bike, you just need some tlc every now and again, so there's no point spending lots of money.
You'll end up riding the bike while the sun shines, then leaving it in the garage when its cold or wet or you're running late or you just don't feel like it today. Eventually it'll live in the garage, growing cobwebs and rust. In this case obviously any money you spent on the bike in the first place is lost, so there's not much point spending a lot in the first place.
The third option is the most interesting, and this is what happened to me. You'll use the bike for commuting and will enjoy it so much that you'll start using it more and more at weekends. And as you cycle more, so you will develop tastes, for example for road cycling or off-roading, trails etc. And its very possible that you'll want to get yourself a bike that is more appropriate for your taste. But of course the difference between then and now is that what the time comes, you'll know exactly what type of bike you want and you won't need anyone else's opinion, least of all a bunch of strangers on SE. So again, I'd buy a cheaper bike now, just one that does the job, with a possible view to buying another bike as and when want to take that next step.

By way of example, the bike that got me back into cycling, I bought from a local bike shop who were having a clearout. It was a reputable make, had a Shimano groupset, but beyond that was nothing special (and frankly I wouldn't have known if it was!). It was old even when I bought it new. Cost me just under GBP100 (USD150ish). So not a massive investment. And I used it for commuting roughly the same distance as you.
After two years of commuting I'd had great use out of the bike, it had paid for itself many times over, but I was ready for something better. In my case it was a no-brainer to upgrade to a fixie - not even a second thought.

A:

For only 3 miles, I would find a used, steel framed, no suspension mountain bike that you can put some slick road tires on there.  And if you're in Boston, go have a chat with these nice folks about your needs and you can learn to fix it, too!  Bikes Not Bombs has been around since forever.  Once you have put a couple months into into commuting, throw down the money for a new ride after you have first-hand experience to know your riding prefence.  

