Now I'm running mirakels kernel-power v41. Stable so far but one problem:

I cannot record a video, the camera app is closing when I try to record a video. Same problem as with Titans power-kernel v40.

Video recording on Titans kernel-power v37 is working.

My N900 is running at 500-900 Mhz. I did some heavy duty tests at 900 Mhz - the N900 is stable at 100% CPU load on 900 Mhz for several minutes.