i've had several 800's stop working after 2 years or so of service (driving a bakpak). i don't consider that too bad, though my hagans and maxi-jets are all going strong after 5 years.
i did have a 2100 explode in my tank. i was using it for in-tank circulation. one night i heard a bang from the other room, looked around and didn't see anything. figured the cat did something. *a few days later* i was moving stuff around in the tank and noticed a piece of plastic the size of a 50 cent piece. it had been blown off the end of the pump and across the tank. i quickly extracted my hands from the water and unplugged everything. pulled the pump out and it was all burned up with exposed copper wires. nothing tripped, and as far as i could tell it was still live. everything was fine though, no short or long term problems that i could notice.