I've been using the latest .6b version and it works like a charm. I've tested out the 333mhz speed on NFU and it does run a bit smoother. The UMD open/close thing can get a little cumbersom but thats only if you're switching between games constantly. It's a great app and I'm loving it.
The only thing I'm waiting for now is external USB memory card/drive support via what ever other program/device that comes out in the future.