Every once in a while my iPad can take up to hours to sync as well. I find that if I take multiple screen shots, camera pictures, and downloaded free ebooks off the iPad, then the sync is again fairly fast. I have a 32GB win synced iPad with 2 gigs video and 22 gigs apps. Syncing usually takes no more than 10 minutes.
I have also found that when the sync progress bar looks like it will take hours to sync, it is best to cancel the backup portion of the sync, complete the new installs, and then clean and backup the iPad.
Works for me :-)