For what it's worth, I've been using GoodReader (http://www.goodreader.net/goodreader.html) to sync music to my iPod Touch running iOS5.
Pro: GoodReader syncs over wifi as a WebDAV mountpoint. This means that you can just copy music files to it like any other folder.
Con: It will only play the files within the folder structure that you supply. Unfortunately, this means that it's hard to make playlists.
This is definitely not a perfect solution, but it's the best workaround that I've found for now.
I wonder whether there are other iOS apps that allow syncing like GoodReader, but also can re-organize files as a fully-fledged music player.