I am Iko, and I often use Kirby (I almost only play 1v1 for glory). Sometimes I use Link and Greninja also, or other characters when I want to try something new.
My win/lose rate is about 50%, that's because I'm still studying the strategies to beat all the characters, and I lose a lot of matches because of this. Today, I managed to defeat a decent Little Mac using Kirby, and it wasn't luck; I finally managed to counter most of his moves. Some characters like Olimar and Dedede are still a pain for me, but I'm searching for their weak points. Even Charizard is a pain using Kirby, I got killed by a noob that spammed B-side just because Kirby is too slow to avoid the attack, and dodging is impossible with the control delay; I can only shield but it ends with my shield broken.
Ironically, I have more problems with slow and heavy characters with big attack ranges than with fast characters like Sheik or Zero Samus.
Anyway, I don't play online very much I'm still completing some boring achievements in the single player mode, and I don't want to use hammers.