AFAIK there's no real issues with Wifi, it disconnects randomly at night when the phone's idle (along with 3G) but that's because HTC put in some stood e power saving profile that shuts those connections down at night and gave users no option to the schedule... You can easily disable that once rooted or even without root thru a paid market app.
Personally I think it was one of the sillier changes in Sense 4, between 12 and 7 I'm either at home with the phone charging (or soon to be) or I'm out partying and the last thing I need is for data to drop in the background and then make me wait for a reconnect when I need it. Almost as bad as the over aggressive memory management if you ask me.
I work 3rd shift and have a hell of a time keeping my phone tethered to my computer. I keep losing my 3g connection, are you saying there is something that can be shut off??