I loved (or love) it too.
It's still plugged in my N64 next to the TV right now.
Apart from the single player game being excellent, the fact you could have multiplayer against 'sims' really swung it for me as I live quite far away from my pals and it really made a difference. Especially the upgraded GoldenEye levels.
EDIT - Ooooh, what was the level, might be that one ^ Area 51 part 2 with the crate where you could go get the Phoenix gun from a hidden bit upstairs?
Also, you come down in the lift after you get it, you can put Xray Vision on, see the blokes outside the lift doors, set the Phoenix to 2nd function and when the doors open you shoot the floor. Wicked.