I've had absolutely no problem using my phone in any regards while it was charging. Sometimes I check email & news while laying in bed with it connected to the charger and I don't have any problems. Here's the one thing I seem to be doing different than a LOT of people: I'm using the old charger that came with the HTC Titan. It's got about a 3' long cord and a snap-shut wall unit so you can flip the prongs down when you pull it out. It seems that a LOT of the charging and heat issues come up when you use the charger that came with the Touch Pro.. although I can't comment (and don't want to - seems like a huge overheating risk right now) on that because I haven't even taken that charger out of the plastic
Experiment with different mini-USB chargers and see if the same problem comes up. Granted mine's an Alltel TP, but I don't think that should make any difference...