I've tested your patch, and there are some great improvements from the original phoenix 1.50 miner indeed.
My 6950 gets improvement.
My 5870 gets improvement.
My 5850 gets improvement.

But I have noticed a regression with my 6870 (1005mhz core / 200 mhz mem)

Configuration:
-Using window 7
-Using Catalyst 11.6
-Using the aoclbf 1.74 frontend for phoenix 1.50
phatk
Vector
BFI_INT
Aggression 13
Work size 128

2011-07-03 kernel: 317 mhash/s (all 3 number are peak value)
2011-07-06 kernel: 283
2011-07-07 kernel: 283

...Needless to say, something bad happened between 07-03 and 07-06. I hope we can get to the bottom of this. If you need me to test something, I will be happy to do what I can for you.

-DiamondPlus