Right but when iOS4 was released it introduced persistent wifi, and it worked for me, when I took the iPhone out of sleep it was already in wifi but no longer.
EDIT - confirmed on both Apple's website and a chart on pocket-lint.
Can't post the links as I don't have 10 posts, but I do know for certain it worked on 4.0 and there is proof of it.
Last edited by XyresicPsych; 07-16-2010 at 01:08 AM.
As long as you know you have wi-fi, how about if you have Wi-Fi "on" in the network settings, and turn cell data and 3G "off" in the settings. The phone then can't revert to 3G. You'll have persistent wi-fi, even if it's because of the settings (of course, you'll need to go into your settings and turn cell data and 3G "on" when you want or need them). [Iphone 3G, ios 4.0.1 here]