Like others have said, I think its doing pretty well. The deluxe and vehicles are the first to go around here as well, and are often completely gone (vehicles in particular). The basic line and Adventure Heroes seem to be selling decently too. It also seems like the Raiders stuff is going a bit quicker right now too, although its all selling. It was already mentioned, but the next couple weeks should be more telling. I saw a fair amount of Iron Man stuff out on the pegs until the weekend it was released, and I don't think I've seen a figure since, aside from maybe the Tony Stark/removable armor one here and there. That's when you see if a line will take off, after the movie is out. By comparison, the back endcap at Target is still packed full of Prince Caspian figures, so I don't know that those are selling much.
I also think that if the line makes it until the end of 2009, that will be a great success. Unless there is another movie, series, cartoon or something in the pipline - they should be able to get the four movies pretty well covered in that time frame. Heck, the lineup this year isn't too bad, and an additional wave for each movie should get us most of what we were hoping for. I haven't seen kids looking too closely at the figures yet, although I've seen several look at the whip. That role play stuff just seems really popular with the kids.