Just tried the 2013-04-10 version on my GTX570. Upped the speed for me too.
Autotune output:
http://pastebin.com/YgtHLWeC. Selected config 30x7 this time, promising around 180KH/s. After a while it is doing 175-178KH/s, pool reports 172.
GTX570 - 30x7
Win 8 x64
314.22 WHQL driver
stock: 732 core, 1900 shader
After 10 minutes, still no stales (yay!!!)

[2013-04-11 20:03:51] GPU #0: GeForce GTX 570, 1491840 hashes, 179.38 khash/s
[2013-04-11 20:03:51] accepted: 50/50 (100.00%), 179.38 khash/s (yay!!!)
The 2013-04-09 version gave me config 120x2 most of the runs, and did 145-150KH/s.
I have an old PC laying around here too, with a 8800GTS 320MB.

Will try to get that online too.