I use it for all the N64 Roms.
it's best to use the GCN R Button for the N64 Z Button though, as the GCN Z button is a little awkard to access, especially for games that use it alot like Goldeneye.
Works well with N-RAGE Plugin, u can use the analogue C-Stick to map the up/down/left/right to the N64 C Buttons.
However I have read some people had calibration problems with the adapter. And the biggest problem is that the included software doesn't have calibration.
it only lets you test the Gamecube button functions and it's rumble.
my R Button experiences a slight flucuation in pressure (as it is analogue) when pressed, which can be a problem for some N64 games (but I edited the NRAGE controller setting file to counter-act this).
But the GCN is one of the best controllers and being able to use it on the PC is great.
You can use it with PC games too of course, and for PC games that don't allow joystick button mapping, u can use a program called JoY-To-KeY that will let u emulate the keyboard and mouse with your controller
