I haven't noticed my phone get too hot while charging it. I use the USB cable it came with to charge it from my PC most of the time, and then I use my old LG Rumor to charge it from the wall.
I have only noticed it get really hot once, and that was when I had the display settings on "never off" while I was downloading about 1gb worth of data over 3g. After about 2 hours the battery was down to 15% and was exremely hot.
I'll play around with the System Panel app and see what happens while charging it with both the PC and the wall chargers.
EDIT: This System Panel app is pretty cool. Right now the battery is at 72% and 27.5 degrees C on the USB/PC charger. Does the app also tell you data speeds over the network (3g, wifi, 4g, etc.)? It has all kinds of cool information, along with it's built in task manager, it would be nice if it had that (paid version maybe?).
"The only easy day was yesterday! Hooyah!"