I thought about upgrading to F16 in November, but btrfs wasn't ready yet, so I'm waiting for F17. While the other upgrades may be pretty cool, btrfs is what I'm really waiting for.
I’m going to start (pre)upgrading every Fedora Release. Preupgrade from 14 to 16 went incredibly smoothly and I can only infer that jumping 1 release will go even better.