Correct - you need to flash the kernel anyway. I use my new kernel daily, without any problem (except the one I already have with the old kernel, like qte crashing on some qcop instructions :-)
I recommand using the battery applet instead of freqchangeapplet, which doesn't look good on the 6000 screen. Moreover, the battery applet can be called from a click on the taskbar (no need to start any app) and automatically set the cpu speed to the one you want when some conditions are reached (ex: charging, low battery)