Finally got around to watching this one tonight.
There is some problems with the framing, I only spotted it because I was looking for it based on Brett's report. It's not a "floating" anything, I think it is some kind of artifact of the conversion process. I took the glasses off, and the entire edge of the frame was blacked out, not just one eye (as it would be if they were trying to reduce artifacts on negative parallax elements, and that did happen in a few scenes, so I could see the difference). Sometimes left, sometimes right, and I think even occasionally both, it became slightly windowboxed.
But, honestly, I wouldn't have noticed it if I hadn't been looking for it. One of the downsides of reading threads like this before actually seeing the film in 3D (I saw it 2D in theaters).
On the whole, I found the 3D quite enjoyable. Subtle, for the most part, good depth to pretty much every scene. A few good pop-out moments where they counted. Definitely the "preferred" method of watching the film, IMO.
Welcome to Rivendell, Mister Anderson.