I guess that Your Vegas was one of the most recent adds, and an excellent one at that. They have a bit of a Killers/Depeche Mode/U2/Coldplay sound. "A Town and Two Cities" just came out about a week ago, and has a well produced, big sound. I'll probably be there at their set.
When I saw that they got added I was pretty excited. I've been listening to them for a little while now (before they were added) and it makes me happy...just a little more diversity in the music at Bonnaroo!!