Do you have a LensCrafters store, or some other eyeglass-store near you? If so, you should pick up a bottle of eyeglass lens cleaner and a package of disposable lens towels (they're packaged in a kleenex-style box). The lens cleaner fluid is a perfect mixture of exactly the stuff Apple recommends you clean the screen with, and the towels are anti-static, anti-lint and are made to scrub just enough to clean without scratching anything.
It's also way less expensive than the Klear-screen stuff you order online: a 3 oz bottle of the Lenscrafters cleaner is only about $3-4.
They work extremely well on MacBook Pro screens, cell phones, and any other electronics with sensitive glass/plastic that you want cleaned well but want to avoid scratching.
And incidentally, they also work well on any eyeglasses or camera lenses you have laying around. 🙂
They also sell packages of pre-moistened disposable towels. I've found that they're decent, but don't work as well. They work okay if you're on the road or something and don't want to pack the huge box and bottle of spray cleaner and towels, but I wouldn't recommend them for everyday use.