I did it once. A fantastic artist friend of mine designed a special one for each member of our group. The people at the con loved it, and came up to us a lot to talk about them. The best part was that we got to talk up our friend's art, as well as look super cool.
So I'd say yay, as long as it's awesome.
Looking forward to Anime Matsuri 2011
Going as...Ciel! ^.^
Currently working on: Ciel's blue dress jacket --- 10% Complete