Very fun but...
As someone already mentioned, I was really annoyed by, for the lack of a better word, the physics engine. Often I would be sent flying to my instant doom when I was at 0% damage, while other times my opponents (and sometimes myself) would barely budge when at 50%+ damage. Also, damage seemed to accumulate much too quickly, a couple blows enough to top 60% sometimes. Not to mention CPU Pikachus always managed to recover, unless I was lucky enough to hit them directly off the stage before they had a chance to move.
Another thing that bothered me was the movement of certain characters. I don't know if it was intentional (I hope not, since it makes no sense), but I've noticed four characters (Tails, Link, Captain Falcon, and Pikachu) who's sprites rotate on an axis way far out from their bodies (there might be more, I haven't unlocked anyone yet). So far out, in fact, that often I turned to try and hit an enemy that was right next to me I ended up ON THEIR OTHER SIDE.
Finally, I was rather annoyed by the limited nature of the move sets. I understand that was due to the fact that all the moves were bound to a single button (a choice that I do not understand at all. Was it too complex to use two buttons, or was that your intention from the beginning?) but come on. Fox's Fire Fox move was only usable in the DOWN direction, why? Ignoring the fact that Fire Fox was always a recovery move, it limited the technique to a very small set of circumstances. I'd go on, but my mind has run out of specific examples.
Oh, and the FAQ page isn't loading on my computer. Is that just me, or is the link broken?