Yes, I have Overclocked N900 to 1000Mhz( so far.. I have tested 1100Mhz without problems.) and MyPaint speed is improved very very... much...

I use Titans kernel | 2.6.28-maemo22 and
Desktop Command Execution Widgets for switching clocks on the fly.

When using MyPaint there is no heat problems maybe because CPU is not running all the time at full speed. I noticed speed improving at 900MHz to 1000MHz. I know that device might not last so long as running at normal clock, but difference is so huge that I do not want to go back to the slowmode .

I can use complex brushes now and they react very fast... now. It is such pleasure to draw and paint. Difference is dramatic. Other benefit is that you can use bigger canvases without much lag.. about canvas size 2500x1600px. is still very usable. (Tip. when using big canvases = high zoom out level and you want to rotate canvas.. zoom in and rotate then... it will happen much faster this way).

I do not recommend overclocking because each device is different. But..

MyPaint was my only reason to overclock

And when I am using devices "normal" things I drop the clock to default 600Mhz. Because when using GPS there might be a problems with heat.

Oh.. more offtopic
I tested today Easy Debian LXDE and GIMP and it works wonderfully with 1000MHz clock.. only thing that I miss is Pressure Sensitivity ... I hope that someone make it work with GIMP. But at least I can edit MyPaint paintings with it. Cropping and Unsharp masking maybe.

Now I am waiting to see some doodles..
So happy doodling... dude.

Tone