About the idling issue, running 900/500 here:
That's 9.8%, 0.2%, 3.8%, 0.5% and 95%, respectively. Measured after reboot and idling for a little while, no apps running. Looks very cool Enable 2G mode, kill WiFi module and you'll get more than 7 days of pure standby time! (I got just 7 days with stock kernel a month ago!)

Someone mentioned that 2G radio was not working. I just made a quick test call in 2G mode, and it worked just fine. Also, a call was made in 3G mode, and it also worked fine. (Also, during this test I noticed that using 3G radio does not cause static into my speakers! Woo!)

Menus run very smooth now. Just as it should be, IMHO!

No difference on Angry Birds, but Bounce Evolution appears to run smoother now...

No heating up. I've been playing some videos here, and the device doesn't get noticeably warmer with 900/500 kernel than the stock kernel...

The most noticeable boost is in Application Manager. It no longer thinks "too long", but feels a lot snappier. And MicroB is now even more awesome! Hey, I think I'll try Firefox now

The firmware problem I read before flashing, so when PR1.2 hits the shelves I'll just reflash the whole dang.

Finally, a big thanks to Lehto for tweaking the kernel!