"Bag Head" Spider-Man is essentially Peter Parker in a Fantastic Four uniform with a paper bag for a mask. There was a period of time in the comics where Peter had lost his costume, and made due with this. I think it is pretty cool that we're getting a figure of it, and hope I can find one.
I'm wondering more about the future of this line. I have the next (small) wave preordered with Prof X, Jubilee, and Blastaar, but I don't know if we know much beyond that. Also, I see some info has popped up online regarding some of Hasbro's other Marvel lines heading into 2013...http://idlehands1.blogspot.co.uk/2012/11/hasbro-and-marvel-into-2013.html
Looks like, if this is accurate, we'll be seeing a 3 3/4" animated style line for the upcoming "Avengers Assemble" cartoon, as well as 6" and 3 3/4" lines for the animated Ultimate Spidey cartoon. Also, there is some info on Iron Man 3 toys, and they mention some sort of "cross building" figures where you can switch parts, etc. More at the link. Factor in a likely Thor line later in the year (and I'm not sure about anything for the Wolverine movie?), and I wonder how many resources will be put towards Marvel Universe (or Legends for that matter). I know there have been rumors in the past of MU slowing down/ending, so who knows. I guess we've had a good run regardless.
EDIT: And then right after I post this I see that BBTS has put another wave (Hercules, Puck, Nighthawk, Nova, and Angel) up for preorder.