A few months ago when I was using/testing radeon on Arch Linux, activating dynpm helped a lot with temps compared to before(could be a bit better though ..).
But the screen flickered often when he card was reclocked and it was .. annoying ...
I still had better temps with Catalyst.
Maybe it's better now though, it's not so tough to test your distro vanilla radeon and your mileage may vary(better or worse than me). But I think if there was a big breakthrough in this sector, I'd have seen it here on Phoronix ..
