Reasonably happy with my Defender for what I paid ($30 shipped or so, amazon).
I can tell it's been cheap'ed-down a bit since the one I had on my old Evo4G, but it's OK for the money. If you are thinking about an extended battery, wait and get it and the seidio case that fits it at the same time. Not cheap though, relatively speaking.
I will say the screen protector, while integral in keeping moisture and dust and scratches off the screen, is significantly more reflective and annoying on this phone than my last one. If I was outside a lot I might be annoyed enough to try something else.