Settings --> iCloud --> Storage & Backup --> Manage Storage --> xxx This iPad will show you backup options = how big the next backup will be and what is taking up the most space. You can turn individual apps on or off in the backup. Camera roll was my biggest which I've disabled as everything gets sent to my mac via photostream (oooh no, all the photos, I want to delete, damn you apple, haha).
When you select iCloud backup a little message pops up to tell you that it will no longer backup when you sync to iTunes. Over the betas I have found it useful to disable iCloud backup every so often, take an iTunes backup, and then go back to iCloud backup.