We've used the 4 omni wheel holonomic for a few years now. We love it and it's a great system. It's super simple to build,weighs very little, and not that hard to program(provided you know basic trig and a little trick with the system). here is our last year's bot during practice and a game match:
practice:
https://www.youtube.com/watch?v=lE8Q...7xo1Oi08f0dphg
actual match:
https://www.youtube.com/watch?v=Kr3jjJhHSsM
i also have a few vids uploaded of a swerve we are prototyping for next year. While the holonomic system works great for us we aren't very fast and get pushed around by pretty much anyone.