Making a character hard to animate doesn't excuse the shitty animation. If they can't do a good job... DRAW IT DIFFERENT and animate it well. If you want to draw pretty and not worry about animation, don't make a TV show, that's what comics are for.
Avatar does a nice job, and I for one like its animation style. They do a better job on their fight animations than any show I've ever seen, and they inject a lot of personality into the characters with the way they move.
If anyone disagrees with me, pony up and link me a show that does better fight animation, with ACTUAL fighting styles represented this accurately.
(FLCL may be in the running for this, quality wise, but there's not such thing as "bass guitar" style kung-fu.)