One more thing --

Even if your friends are checking bags, I recommend that you carry yours on board if possible. It's a slightly bigger hassle at security, but it's much better than having your luggage lost or delayed.

On average, one of my seven associates has their luggage lost or delayed on every other trip (about a 7% chance per person per flight -- which may make us unluckier than average). Since I bought the Aeronaut last year, I've been immune -- but my associates haven't wised up to the one bag concept yet.