I'm using USB 2.0, which is dog slow. My PC is a quad processor, so it's relatively fast. Wish I had BT 3.0 on my PC to match it on my Vibrant. I suspect it would be much faster than USB.
Doubletwist does run multiple applications when a sync is invoked, so it can seem a little slow. From what I can tell:It pulls in Sorting, File, Artist, Album, Song, and other detail from iTunes and Windows Media Server.
It converts the file to an appropriately compatible file format for the Android OS.
It reduces the size of large or lossless files at a ratio of between 5 and 10 to 1.
It does quite a lot, so that's likely the reason for the apparent slowness of the sync.
I have a legacy of using iTunes to archive all my music, and to playback most of my music via Apple compatible devices. So I continue to use iTunes to manage my playlists and my files. Doubletwist fully utilizes the use of iTunes as my music database and server. To be clear, I don't manipulate any playlists or files within Doubletwist. I do all this in iTunes, and DT pulls the data from iTunes. Doubletwist is simply the gateway between the database (iTunes) and my player (my Vibrant). This is the solution for families that have both iPods/iPhones with a ton of AAC and Apple lossless files AND they have a new high density Android phone. It's awesome. It's better than even the dudes at DT claim. Andless is not bad, but is not nearly as scalable to manage the 25k songs I own in lossless format. It's only in the instance that I want to pull some really quality ripped songs to my phone to play.
Here's the punchline; I have about 30GB of lossless files on my internal memory on my Vibrant, though they are reduced. Quality is actually quite good for headphones and a portable device. Not at home, but definitely for mobile use. 30GB reduced to about 6GB. I'm loading up more files.