as do i but to me this acid crap is what the survivor series is to resident evil.
I have AC!D, it's a really different game. It might put you off, or it might not. Just don't expect Tactical Espionage Action it's more like Tactical Turn-Based-It's-Time-To-Duel Action.
But I like the originality of it, that alone for me makes it worth playing. Plus the story ain't too bad and Kojima has put some good ole MGS humour in there too.
A game for the PSP I recommend is Wipeout Pure, pretty sweet game if you're a fan of the series.