I must admit I wasn't sure this would work when I bought it but boy was I wrong. It is great. The fish like it, the frogs like it and the newts love it.
It doesn't need direct sunlight but the light needs to be strong enough to cast a shadow. Once the angle is past 35 degrees to the perpendicular the power drops off rapidly but when the sun is directly on it at midday it looks like Godzilla is boiling out the depths of my pond with a severe case of flatulence.
Not sure how long it'll last but mine's been going great guns for a few months now and I love just sitting there and watching the bubbles.