I have two Macs (Macbook Air 2011 and Mac Mini late 2010) with Mac OS X 10.7.2, both have latest iTunes. I installed iOS 5 on my iPhone 4.
iTunes on Macbook Air is configured to sync Apps and Podcasts, iTunes on Mini is configured to sync music, ringtones and books. Both are set to sync wirelessly.
I synced my iPhone with my Macbook at work after installing iOS 5, apps and podcasts were installed properly. At home I synced with the Mini and got my music back on the iPhone. Apps appeared to be still present, did not check podcasts.
This morning I then synced again with my Macbook Air at work, and the music was deleted. I do not have sync music checked. Of course I cannot get the music back until I go home.
I have not yet moved to iCloud, maybe that will help some, but I have a lot of non-iTunes Store music via CDs...