Well, I can confirm that turning off cellular data does not fix the issue. A ping test shows the phone unlocked, then going to sleep. This is with cell data off. Noted below is when the home button is pushed.
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Request timed out.
Request timed out.
Request timed out.
Request timed out. <pushed home button>
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If I did not have another 4s with iOS5 I would not have found this. The other phone ping tests for over 3 minutes with the phone locked with no lost packets.
Apple, this could be why some people have very bad battery issues, and others do not. If iOS5 was made to sleep the WiFi, and not all phones do for whatever reason, this could be substantial. I clearly have one in my possession that does not, and the battery life is quite bad. ;-)
I do think this should be a user option in the autolock area of settings.
Battery pack for me... I hate my building!
Mike