I used to be a case junkie, and in some ways, I still am. I still read a ton about cases. My first two iphones (original and 3G), I probably bought over 20 cases. So far, with my iPhone 4, I've bought 2, and also received my free bumper from Apple. For my 3G, my most common combo was the Otterbox Defender, with the screen ripped out, and an Invisible Shield on the screen.
Now with my iPhone 4, I have a Clear-Coat shield (similar to Invisible Shield) on front, back, and sides, and was using the bumper. BUT, I just bought the Case-Mate Hulu (in black), and I LOVE this combo ! It's like an Apple Bumper, but the sides are clear, so it really shows off the phone like it has no case on. It really looks sleek, and I really like it better than the bumper, fits the phone better.