Do some hallway usability testing (in the same way you would do code reviews).
Even a really quick "Hey! try this" usability test (if you can call it that) with the guy next to you will make a big difference. The main thing is to have somebody other than yourself try the bit of UI you've just built.
It's amazing how many times other people get stuck using your new UI, and it only takes a couple of minutes (usually) to find the biggest problems.