The HOV lanes that were put in for the Pan Am games are kinda annoying. The fact that you need three people minimum to drive in them rather than the usual two makes it exponentially more difficult to use them for commuting. Even when you do get to use the lanes (wife, kid and I were driving to visit a friend this weekend), they kinda cut in and out of major routes so they only help for very short stretches of the way. It seems like accidents on the road have a much worse effect than they normally do in slowing traffic down.
All that said, I like the idea of them. I'd prefer it if they made HOV lanes standard through all of the major highways in the city (just with a 2 person minimum occupancy). I do think that this would encourage much more car sharing, which is a good thing. God knows, we don't do dick all to build transit that makes sense in this city, this seems like a tiny step in the right direction.