Can't confirm - I also use 500-900 limits (all the time) and it changes frequency as it should. BTW, I don't know what You guys got in your device, if looking @ conky gives You constant 900 - Mine is 4-6% @ 500 mhz, when only Conky opened. I occasionally jumps higher, during swap flushes etc, but only for a moment.

/Estel