So the jQuery team released v2 a few months back and hopefully everyone had a chance to settle in. We have had much time with it, and although it wasn’t the shocker-level changes that we saw happen from 1.8 to 1.9, they dumped support for legacy IE/browsers: 1.10 API is exactly the same as 2.x, less the IE8/9 bits.
Given that most of our clients still run IE8, it will need to sit in the box for a while yet. Now, v2 on SharePoint is pretty much a non-started today due to this limitation. The official MS compatibility charts show IE8 as a supported platform, so it won’t be for another 2 years that this wretched browser is going to finally go away.
If you want to get the most out of JQ, stick with > 1.10.x and be sure you plug your own namespace in when building SharePoint apps, otherwise your customers are going to find nasty surprises when they try and install third party WebParts or Apps!