I'll offer up another solution, TuneSync. I have found it to be very easy and straightforward. All you have to do is install the app on your phone (unfortunately it's not free, though), install a small program on your computer from their website (tunesync.com) and sync the two (have to be connected to your wi-fi). After that, just select which playlists you want to sync and it takes care of the rest, wirelessly. I haven't tried iSyncr, so it may be just as easy. I've heard DoubleTwist recommended as well in the past, but I didn't like it. It was too confusing.