My heater didn't actually explode like btkrausen's, but it shorted out and started burning inside the tank. It was bubbling like crazy and smelled horrible. Luckily I caught it before it burned too long and was able to do a huge water change w/ fresh carbon running to prevent any losses. IMO, I'd just stay away from any stealth heaters. I read the horror threads about a $30 heater wiping out $2500 in livestock all too often.
Oh yeah, there are a bunch of threads on RC about them killing all kinds of livestock. I push everyone away from buying these things. You'd think Marineland would stop making them if they are blowing up like this.