I'm sure many people use Evercoat on here, I do, but I call it bondo because it's easier. They are both body fillers and there are others out there, but bondo has become the term people use when talking about body fillers. Kinda like facial tissues vs Kleenex.
As far as Evercoat, I haven't noticed a huge difference, but I do like it. Bondo brand is also easy to get and cheap at $6/quart. Quart should last you at least two helmets, maybe three.