I have the bumper, griffin reveal etch, and incase snap case. I was never a fan of cases - always used an invisible shield, but I was luke warm about the bumper, indifferent about the etch, but I absolutely love the snap case. Leaves all my ports open, it's rigid, adds grip so it doesn't slide as much and it's slim. My only complaint is that because the top and bottom are exposed, the antennas are a little scratched up, but I've also gotten over keeping my phone in perfect condition - kind of takes the fun out of using it if I spend time worrying about damaging it.
edit: The stand is also a nice add on, I use it when on facetime so I can keep my hands free to work on my computer while video chatting with my girlfriend. I wouldn't pay more than $15 for it, but I also think anything more than $10 is outrageous for any kind of case, so if you think the bumper is worth $30 then the snap case is what I think you should go with.