To be fair, the GitHub for Windows UI looks a lot like the Zune UI, which has been around for a while now. I've not been able to try it yet on my Windows machines, but the screens I've seen look like they borrowed heavily from what Zune had.
GitHub for Mac borrows from a lot of good Mac UIs, and it looks like GitHub for Windows does the same from good Windows UIs. Frankly I find this refreshing. I'm tired of applications that build their own interaction layer and then implement that across every platform regardless of that platform's idioms. Or, even worse: Air apps.
