Since Git Tower v2.0 was released, I've installed a trial and I've been using it on and off in parallel with Git Tower v1.x. In general, I like it. I think it's a fine evolution of Git Tower, I think the UI changes are mostly improvements, and I'm looking forward to using it full-time.
Having said that, I don't think it's ready for prime-time use, at least not for me. I've reported a few bugs already while using the trial, and I'm not the only one. And if you read over the mentions that @gittower has on Twitter, I think that's the general sentiment: looks good, but needs a bit more attention.
There has been a few point releases already (v2.0.3 at the time of this writing) and I expect there will be more. Basically, I'd say it looks like a promising upgrade, but if you're in no rush, it wouldn't hurt to wait a little longer. If you're curious, then download the trial in the meantime. If you really want to use Tower 2, you probably can, but accept there might be a few issues along the way.
Update: I have been using Git Tower 2 for months now and almost all the issues have been worked out. It still, isn't perfect, but I don't think the remaining issues warrant much caution. I would say "buy".