I simply love this mod. Not only it reminds me of the BuddyEX addon from SRB2, but it is also extremely simple and fun to use. Being able to build your own "team" and having the possibility of quickly switching characters during the gameplay is an amazing concept, especially for sm64. I'm glad that someone finally made it!
However, there is a noticiable bug present, but it's nothing major or critical. If you swap characters while there is a wall behind you, your character will pass through it ("no clip" in lack of a better term), fall in the void and die. It's rather funny during my first time discovering it not gonna lie.
I think there's also might be a compatibility issue with the Megaman X mod, since when one of those characters is either being used or loaded as a sidekick, they somehow softlock the entire game when you enter a stage through a painting or a pipe. (You're forced to close the game and re-open it since it doens't let you access the menu, and changing characters through CS does not fix it.)
Those are the only problems I have, but overall, the qualities offered simply overshadow these issues. Honestly this is one of the best mods avaliable on this site in my opinion.