As far as PM, it does seem to work. The core is downclocking fine as far as I can tell, which is making things slower than usual; KMS makes 2D slow as is, so the downclocking is making things worse .
Mobility 3470 here. The first DRM power management patches did just that, slowing 2D to unacceptable levels. Since 2.6.33 + patches, it's become very good, with no noticeable slowness at all. Now, it seems to change core and memory frequencies very fast.
And my notebook stopped hanging with a black screen due to overheating, as well.
Now, I'm just hoping the current power management, or the future advancements, will be enough to cope with the summer's heat.
On my laptop (200M) it works a bit better, in that it's not unbearably slow. Thing is that when the core downclocks, response becomes "jumpy"; the mouse cursor seems to get "stuck" as I move it across the screen, and window animations sometimes leave a noticeable trace behind them. This again, is due to KMS making things slow and the slower frequencies only worsening the problem. Should be better once I move to a newer xserver.
What does it mean? The new kernel dropped about 20C (from 80C to 60C) which is already very good result but I still have a hairdryer instead of fan (it's sooooooo annoying). Maybe with ACTIVE instead of MINIMUM it'll be better? Is there any way to change it?