I don't think I had ever watched this all the way through before, but it's currently available on demand on DirecTV so I watched it last weekend.
De Niro, as always, is magnificent. James Woods falls flat for me, though. That might be because he's made such a career of playing crazies that the whole time you're just waiting for him to go off into his schtick. Very nice to pick out the rest of the cast of thousands -- Peschi, Weld, Aiello, Young.
I thought that much of the present day story was hokey and overly contrived. Does Noodles really have to be led around by heavy-handed clues to jog his memory of his own past? One question to be asked of a film told in flashback is, "Would you watch it to the end in chronological order?" I don't think the movie does (except that De Niro remains watchable).
It's a good movie, but probably a little too complex for its own good. I have the same sort of criticisms of GF2, but not nearly to the same extent.