Plot-wise, there's almost NOTHING to complain about! It might as well be the only instance of a game trying to replicate film that actually works. Great characters, immensely strong themes for such an old game, and some of the best voice acting in the business.
Gameplay-wise, I'm torn. The design itself is amazing, with so many funny details to immerse you into the world, but the way it's utilized feels confused about what kind of game it wants to be. It's marketed as a spy-thriller stealth game, but it also has an obscene amount of schizophrenic boss fights and sequences where enemies chase you down while you're collecting assault rifle ammo like a fat kid eats his MacDonald's chicken nuggets.

I don't want to be too harsh on it, because it is a classic of the fifth console generation, but I wasn't there to experience it at the time so I don't have the nostalgia to back up my enjoyment. I still have two more sequels waiting to be played, and who knows where the quality goes depending on how they evolved with the platform? I'll be looking forward to seeing these characters again (for a while at least before they get replaced by an albino twink).