I think kano is right. At least it was the reason preventing me from updating from version 2.1.2 since phatk opencl code has changed and cgminer had to recompile (or whatever it does with .bin files) it.

I had trouble deleting APP SDK runtimes. Somehow it stayed in the system after uninstall.
Here's what you need to do:
1) Uninstall either APP SDK runtimes or whole Catalyst suite through AMD uninstall utility.
2) Search for amdocl.dll and OpenCL.dll in Windows directory and delete them
3) In case you uninstalled whole suite, reinstall it with custom install and uncheck APP SDK runtimes
4) Download and install needed OpenCL driver. Older version avalable for direct download here:
http://support.amd.com/us/gpudownload/windows/previous/Pages/radeonaiw_vista64.aspx
http://support.amd.com/us/gpudownload/windows/previous/Pages/radeonaiw_vista32.aspx
http://support.amd.com/us/gpudownload/windows/previous/Pages/radeonaiw_xp.aspx
For newer versions - download suite, install and select only AMD APP runtimes. You can backup OpenCL.msi from AMD/ATI temp directory on C: for future use.

You can choose driver version according to needed SDK version:
http://developer.amd.com/sdks/AMDAPPSDK/downloads/pages/AMDAPPSDKDownloadArchive.aspx

G->I->[GPU Num]->[Intensity]

Win7 x64, 5870, Catalyst 11.7, latest GUIMiner (Phoenix 1.5).
After copying v2.0 files into "kernels\phatk" i get this messages in console:
No work is being done.

Here's miner starting parameters:

Your v1.0 and Diapolo's 2011-07-17 kernel works fine.

Yes.
I did it for partial backup, since GUIMiner doesn't support normal backup for Phoenix miner.
So, primary miner get around 90 MH/s less speed, but second one can mine at ~400 MH/s if first one fails.
With 11.6 i got the same 440 with single/double miner config.
With 11.7 i'm getting 440 with single and 430-480 (sometimes it jumps to 530+) with two miners on single card.

I'm using Phoenix 1.5, so i got 100% on single core even when i used 11.6.
No difference after updating to 11.7.

Try to add second miner for each card. I got no difference while using single miner.

Actually i continued mining with two miners config and i got higher speeds confirmed by pool i'm using.
Strange, but it looks like it really works better that way.

I'll continue monitoring and report back later.

-Do you use default poclbm miner or Phoenix?
-What does it say on "Console" tab of your GUIMiner? Copy all except your login data.

PS: What is "incredibly hot" for you btw?

Earlier i used 11.6 catalyst drivers. I got stable 440 MH/s mining speed from my OC'd 5870 with any combination of miners.

Today, after updating to 11.7 i noticed something strange.
While mining with single miner with AGGRESSION=12 i still get 440 MH/s, but if i'll add to that one more miner with AGGRESSION=6 the speed is starting to jump from 440 up to 550 MH/s.

Is that normal?
Did anybody else noticed that?
Is it really the speed changing or just inaccurate calculation?

PS: I'm using GUIMiner, with poenix miner and custom phatk kernel.