I connected mine to my iMac v10.6 and ihad to select "mount as disk". It mounted to my my desktop just fine. Then I went to the Music folder and drug music from my iTunes folder and droppped them in. If the folder wasn't there, I'd just create one for the artist.
I use DoubleTwist too, but I must admit... it's a nightmare and I don't understand it. All of my external HDD's mount, and I can't unmount them within the program cuz it says they are in use. It also says it will sync my iTunes playlists if I want, but I don't want ALL of them.
There may be one out there, and if so, please tell me what it is, but is there an "iTunes type" app for Mac or PC that will deal with music for Android phones. I'm surprised that it's difficult. Some people hate iTunes, but I just dont' see how that's possible! It does everything I'd ever want it to do and more. So far, managing music on my Thunderbolt has been sorta of a hassle. The old drag and drop method worked the best though. Airsync with DoubleTwist takes FOREVER and most of the time it will crash. Even after the newest update to DT that just came out.