Not sure if this is a bug or not. I am using Android 3.1. Basically when I switch the TF into sleep mode by hitting the power button on the side and leave it like that for a while. When I resume, the wifi signal is gone and I can only seem to get it back by powering off and on again. If I do it right away though instead of leaving it sitting for 5-10 minutes it works fine. I've only noticed this when upstairs where the wifi signal is weaker though.
I am going to test it near the router next and report back. I have wifi set to be always on in settings. I also use the built in screen lock.