I've said this several times on this board, but I absolutely hate the multiple characters in the DS version. It completely ruins the sense of spontaneity and freedom the original game had (which was THE ENTIRE POINT of the original game). When I'm playing Mario 64, I shouldn't have to stop and think and plan out which character I'm going to use before I enter a level, and then trek back to a room to go through a door to switch characters. I should be able to just jump around and have fun.
If you didn't plan ahead of time exactly what you were going to do in a level, you pretty much had to go in as Yoshi, since the star might require Yoshi's abilities and there are no Yoshi hats, but if you're Yoshi, you can't wall jump out in the castle. Actually, I think only Mario could wall jump, which was stupid.
And it didn't add anything to the game at all. The different characters all put together had the same abilities as Mario in the original, just less conveniently.
Multiple characters should be like in SMB2 -- they have their pros and cons, and some are better on some levels than others, but you can beat any level with any one of them.
Anyway, happy birthday, original SM64!