I have high hopes for cen64 in the future, as well as for Mupecan64 (by hacktarux, same person who made mupen64), but at the moment they're both pretty worthless. That's not a knock against their authors, they're just too young to be usable at this point.
Angrylion's plugin is pure software, and too slow to be a widely usable solution. Pixel-accurate software renderers have their place, but the world does need a good hardware renderer for people who don't have top-end machines. I think a lot of people also would not care for it rendering at native n64 resolutions (that's a hit to accuracy that I'm willing to take).
I was not aware that mupen64plus was available as a Retroarch core. I will have to check this out; I have only tried to use it command-line before, or with its many (often broken) frontends, and it's kind of a pain. As I've been using Mednafen-PSX through Retroarch for some time now, I really should've known this. :/