I think he'd be livid - over what's happened to Sharon, over the state of the Marvel U (Norman Osborn in charge, the SHRA still around), over the way Tony's been treated (because even angry with Tony, he still cares about him) and also horrified and grief-stricken/devastated over Secret Invasion (the fact that people he knew and trusted were skrull plants) and most especially over Jan's death. Clint and Thor's return from the dead would make him extremely happy, but he'd be discovering that he has two of his oldest and closest friends back at the same time that he's finding out that he's lost another of them -- we're talking serious emotional roller coaster.

Not to mention that he'd be coming back to find that he's effectively been replaced. I mean, even though he might very well run around as "The Captain" for a while again, or possibly borrow Clint's silly "Ronin" identity out of anger/protest at the government, Captain America is still who he is, and even though he'd probably have given Bucky his blessing to take his identity had he known, there's probably still going to be a little part of him going "But how could Sam/Tony/etc. replace me?" A very small, quiet part of him, mind, and he never actually say it.