we've done in on christmas day and the crowds are CRAZY!
on the same trip however, we saw it a few days before christmas and it was much less crowded and still just as fun.
it's a beautiful parade, and my favourite float is the one with chip and dale -- smells like fresh baked cookies!!
but, my suggestion is to see it ahead of time.
just one little tip: christmas day, we got there at opening and went to toontown -- it was deserted and we got to see winnie, tigger and eeyore by ourselves! it was amazing! (of course, at the time i was 21 and my sister was 19, but whatever! it was still fun!)