alright, played it for an hour. let's get one thing out of the way: this game does NOT hover between 30 and 60 fps. i don't know who originally said that. it never even comes CLOSE to hitting 60. i was convinced it was locked at <30 until i went into first person in a narrow cave with no other models around, when suddenly it seemed to briefly jump to 60 fps. this was the ONLY instance of this happening and it went back to 30 fps as soon as i changed the camera back to normal. whenever rayman is on screen (which is 99% of the time) the game will be at 30 fps and below. the framerate drops quite frequently and not just in certain areas. so be prepared for that. it's not what i would call a stable framerate.
i bought the game because i'd never played the original, so i figured it'd be worth it even if it turned out to be just a subpar port... which it is in a lot of ways. it plays fine, the controls work great and i'm definitely having fun with it and it's pretty for the most part as well. but from the moment the title screen loads it's clear that this is just another ubisoft rush job. the hud, the loading screens, the cutscenes, the barebones use of the lower screen are just the first signs. then there's the strange audio glitches and the music that was obviously mixed too loud and sounds noticably distorted at times (turn down the music - not the sound fx - in the options menu right away!). some effects are still much quieter than others and unless you turn down the music almost all the way you can barely hear them, but rayman's steps and voice for example are always fairly loud. just a poorly balanced audio mix i guess. the music also tends to suddenly cut out from time to time. of course i have no way of knowing whether some of these audio glitches were present in the original, so take this whole thing with a grain of salt.
one more thing about the visuals: they are definitely darker overall than in the original. i just looked at a youtube video of the ps2 version which seems quite a big brighter. it has nothing to do with any sort of dimming effect from the 3d screen though, since a) the screen is just as bright with the 3d turned off and b) other 3ds games can be extremely bright, with colors that really pop (pilotwings resort etc.)
i'm probably making it sound worse than it is, as i'm really enjoying my time with the game. the problems i described are probably not that noticable to most people. it's NOT a broken game, far from it. but it does have a handful of flaws. just be aware of that if you intend to buy it. (it's definitely about a 1000 times better than the horrific ds port, which i bought too and couldn't stand to play for more than 20 minutes.)