Ok, my findings so far:
5850 on SDK 2.5
2.2.7 ~400MH/s with phatk120213
2.3.0 ~320MH/s with phatk120222
2.3.0 ~400MH/s with phatk120213 *but* lots of HW errors!
So it seems the hashrate drop is in the kernel changes?

The old kernel is simply not compatible with the current one.
Well this makes me fucking angry. All I can do is shake my fist even harder at ATI for the changes just SHOULD NOT CAUSE THIS as they're meant to be trivial changes. Well more fucking quick fucking releases to deal with fucking ATI fucking fail. Rollback phatk fucking time.
Yeah and people were bashing me when I was screaming Nvidia.
ATI will probably never fix these bugs in their SDK and drivers.
CPU bug, SDK 2.6, 8 GPU hardcoded limit, needs to be linked to xserver at all times.
If only Nvidia would wake up and see that we are waiting for the 4608 shader dual GPU.
Hopefully the integer performance is much better this time around and they implement a variation of BFI_INT or bitalign.
So when will you release the fixed cgminer ?
Thank you !