I actively play my N64. In fact, I got back from a three day school trip today, and we spent over 20 hours on the N64 with games like Super Smash Bros., 007, and Mario Kart.
I still have mine, though it's not currently hooked up. It's in a box in the closet with the PS2, Snes, and Gamecube and all the controllers and powerbricks. I had it set up for a while, but I didn't play it often enough and didn't want it to get dusty.
If I owned one I would play it. I have been thinking of buying one but there are too many 3DS, Wii and Gamecube games that I want to play so I would have no time. Once I can get those systems straightened away, I will probably buy one and end up playing it fairly regularly.
I don't have an N64, but talking about old-school systems in general, I find that I have zero interest in playing them after I got the newer PS3 hooked up. Maybe it would be different if I had more space in my TV board to hook up 2 consoles at the same time, but as it is, I'm too lazy to connect the PS2 and bother with all the cables.
That, plus the giant backlog of current-gen games I have.