I a similar problem, and after trying out a few different apps, I found that TuneJack worked great for me. Not free, though. Cost me 10 bucks. It'll scan your iPod and iTunes, then sync iTunes to your iPod. I had only lost my playlists, though, and it worked perfectly. It also duplicated some songs (about 10 out of 7000) but put them into a separate playlist, as well as the main library, so they were easy to weed out. Turns out I had updated the tags in iTunes on those ones, so I guess that would show it at least reads tags, but I'd check about the copying tags issue to be sure. I imagine it would, though, as I'm pretty sure the tags are contained in the song file itself. Get it here.