i had a theo heater. ran for 2 years no problem and kept the water warm and temp stable. it was mostly black with a some silver and red, although most of that color faded over time as the water broke down the outside paint.
when i worked in a lfs, we had many heater on the tanks. the aquaclears were ok, but they broke easy. the visi therms were nice and many lasted a long time. they even held up well during tank cleanings when they were above the water line. the hang on ones broke alot.
just so you know about the tetra whisper submersibles, they have TWO lights- one red for when the heater was working and a green light for when the tank was at desired temp.
hth.