I'm a bit torn between using my new iPhone 4S as-is or buying a case. For the past few months I used it "naked" with no case whatsoever, and I can say that it has much better grip than the 3S because both surface sides are flat and a kind of glass that grips easily. I'm still worried about two things though: accidentally dropping it, and battery life.
So the first case I looked into is Mophie juice pack air (
http://www.mophie.com/ ), white to match the phone. It would double both as a protective case (back and sides, and there's a front bezel for when it falls flat on the front surface) and as an additional battery. I don't worry too much about doubling the iPhone's battery life, but more about preserving the built-in battery (at the cost of the Mophie's) as much as possible. The "air" version of the case is thin enough to be used as if it was a "normal" case.
The other possibility is to get the LifeProof case (
http://www.lifeproof.com/ ). Its primary purpose is to make the iPhone waterproof, and also protects the phone from dust, snow and drops. And by "waterproof" they really mean it: shower, pool, and so on. The downside is that it's a little bit clunky, headphones may need to use the provided connector to work, and once in the case you should leave it there for as long as possible. It may be overkill (or overprotective, actually), but then I can't find anything that protects the phone better other than a separate waterproof pouch.
So, which is more important? Protecting the phone when it's pouring outside and I forgot my umbrella, or extending its battery life?