Aye, it has definetly aged and shows it. The original Perfect Dark is unplayable these days, i can't look at it for more than a few minutes without getting a head-ache or something.
I never as such had issues with the framerate when playing Goldeneye and Perfect Dark multiplayer on the N64, even with 4 players. Ok it did lag a bit in places, but other than that, they were fine for me.