On the "Cap lifting Thor's hammer" thing -- I think I fall more into the camp that would like to see it, but not in the first Avengers film.
Because I can't help but think that, well, sure, everybody posting here will see The Avengers having seen the Thor film... and indeed, having seen and in many cases memorized all of the films that lead up to TA. Which is great, but on at least SOME level, Marvel Studios has to make a story for the film that can be accessible to those in the audience who missed one or more of the lead-up films.
So those of us who've seen "Thor" -- and who know TA:EMH, and the comics, and all that stuff -- we all know deep down what it means for Cap to be able to lift Mjolnir. But, within the context of The Avengers... I just think they need to put some stuff in the first movie that will establish it there as well. That might seem like belaboring the obvious to us, but it's necessary.
Look at it this way: The Avengers film will need to make it clear to the characters who weren't in the Thor film what the deal is with Mjolnir. I don't need it to take up a lot of time, but man, I'd love to see Hulk try to lift the hammer and fail; and I'd love to see Tony being driven crazy by something that defies scientific explanation. So that by the time Cap lifts it, everybody around him (not just Thor and Loki) really have an idea of what an accomplishment it is.
I suppose the first film could do that by putting in some "others try to lift it and fail" moments as early as they can, and leaving Cap lifting it for the end. But that still seems rushed to me. Let Thor have one entire film where he's the only one who can wield Mjolnir. (Especially since even he couldn't wield it for the entirety of his own film.)