Bryan -
So if I use iTunes as the repository, then i can set up my ratings and playlists in that, and SB will then import/monitor those for its playlists, saving me the hassle of maintaining two databases? By interface for the player, do you mean I can have the SB software open, and select songs to play directly from my computer without having to use the remote? Sometimes that would be more useful, like when I'm using my computer. If so, what you are saying is awesome.
iTunes can be tricked into playing FLAC, and I did it once with a drag and drop converter. Basically what it does is wrap the flac file in a Quicktime friendly video shell, and play it back. You can't use tags that way though. I use a program called XLD, which is a free download, that lets you convert losslessly from FLAC to Apple Lossless, or any other format really. So I can download FLAC files (which are prevalent on the net) and play them in iTunes as ALACs (which almost no one uploads). So basically I have an apple lossless library that I can convert into flac if need be.