Hey lee63... I run my 8800GTS @ 720/1800/2000 ( core/shader/mem ) for everyday use.
Max stable has been 800/2050/2200 http://www.nvnews.net/vbulletin/show...&postcount=900
The shaders really do make all the difference.... core overclock is no where near as important as shader as they bottleneck the core.
Lets see some great numbers.