The "heat" issue is hard to pin down. Lots of chatter about it in the various forums. But it's all extremely nebulous and vague. "My SMP gets hot." OK, what does that mean? No one ever talks in specifics. If someone said "I measured the temperature and it was 130 degrees, OK, I'd buy that.
I think, too, that many people that report "heat" issues are actually plugging in USB devices that get hot, and that heat transfers by conduction into the WDTV case. Most USB flash sticks aren't intended to be accessed with frequent read/write 24x7 operation (which the SMP does depending on how it's configured) and do get very hot (measured one at close to 150 degrees on the metallic USB interface once.)