My ex-gf's Eris started overheating EVERY TIME it's on the charger.
It started when we put in the Seidio 1750. She charged it overnight, and woke up with the SetCPU warning in the notification bar, a notification on the screen, the phone software frozen, and the phone so hot, that she LITERALLY couldn't even touch it. She unplugged it and carefuly took out the battery and let it cool.
EVERY day this has happened to her phone, every time she charges it. She wakes up in the morning - the phone is software-frozen and overheated. Every time. Too hot to touch.
THEN, one day she woke up an hour or two after she passed out, and her Eris was on fire. Literally. It looked like the phone was a Zippo. If you look at the OPPOSITE side of the volume buttons, it's right above where the upper volume button would be (just the other side). Even through a blue case, the fire was coming out.
She grabbed the phone anyway and burned herself, not believing what she saw. The phone looks completely melted at the area where the flame was, both on the normal eris case back, and the blue aftermarket case from Verizon.
What's great is, the phone has NOT overheated while charging, EVEN ONE time, since this fire.
The point is that, every single time, the phone was absolutely and unequivocally SEVERELY 'overheated' to a point beyond human touch (for about 3 months, almost every single night), with 0 hardware consequence (unless you count the fire).
The phone is functioning uninhibited, with nothing wrong whatsoever, to this very minute, and with a new back and case, you couldn't even tell there was ever fire.
The point is that this whole overheating thing may well be overblown. Her phone has never sustained any functionality loss WHATSOEVER after months of overheating every single day. It WILL reduce the life expectancy of the battery. But it looks like HTC used better materials for their solder points than, say, Microsoft did for the XBOX 360 (hence the 'towel trick' completely unscientifically working to re-melt solder points).
I'll post pictures at some point. I'm trying to get back with her anyway, so I may take pictures regardless.