UI.X is so ubiquitous that I wouldn't be surprised if someone thought it was stock XenForo. It's for good reason of course, it's a lovely theme.
Personally I don't like to use premade themes even as a base, I like making something totally custom. That said, I think @Sage Knight 's styles go under recognized -- they're really nice!
On vB I used to rebuild the style from scratch for every major version, and do individual updates for point releases. But I just don't have as much time for forums any more - so that merge tool will come in handy!