My story, fwiw:
iPhone 4 (ios 5, 9a334) syncing to MBP with itunes 10.5 (141) was hanging on "waiting for items" on Genius data
I tried
1) Disabling Genius: Hang switched to "Waiting for changes to be applied" (ugh)
2) delete voice memos (I had none): no effect
3) stop syncing photos and books: no effect
4) 5-sec phone hard-reset: no effect
What finally got the behavior to change was
--All of above plus:
--Activate airplane mode, then do 5-sec reset
--Quit iTunes and turn off airport on macbook pro
--connect restarted phone via cable
--run sync
It got the podcasts and tracks synced (what I was originally hoping for) but now the sync is stuck for 15 minutes on "waiting for items to copy" for "Syncing Artwork..."
I am going to do a factory settings restore and restore from backup when I get a chance, but I hope Apple can figure out what's up with this one... I like the ability to keep using my phone during syncs, but it's somewhat less valuable a feature if the syncs never complete