user3029: What is Bitcoin's locktime feature and what are some example use cases? 
And how can a user make use of this new feature? Is it in any gui wallet? And how would one use it in the command line if its the only option?

user33258: Like a cheque with a date in future, a Bitcoin transaction with locktime cannot be unlocked (read cashed) before that date. The definition in bitcoin.org is pretty clear

Part of a transaction which indicates the earliest time or earliest
  block when that transaction may be added to the block chain.

Sample use case is a cautionary deposit. For a great example see micropayment channel protocol implemented by bitcoinj and described here: 
https://bitcoinj.github.io/working-with-micropayments

3029: <p>What is Bitcoin's locktime feature and what are some example use cases? </p>

<p>And how can a user make use of this new feature? Is it in any gui wallet? And how would one use it in the command line if its the only option?</p>
 33258: <p>Like a cheque with a date in future, a Bitcoin transaction with locktime cannot be unlocked (read cashed) before that date. The definition in bitcoin.org is pretty clear</p>

<blockquote>
  <p>Part of a transaction which indicates the earliest time or earliest
  block when that transaction may be added to the block chain.</p>
</blockquote>

<p>Sample use case is a cautionary deposit. For a great example see micropayment channel protocol implemented by bitcoinj and described here: </p>

<p><a href="https://bitcoinj.github.io/working-with-micropayments" rel="nofollow">https://bitcoinj.github.io/working-with-micropayments</a></p>
