When I watched the first ep of Excel Saga, I thought Excel (the character and the series) was truly the worst thing to ever happen to anime. She was annoying, stupid and vulgar; the series didn't make any sense. However, after watching the second ep, when I stopped laughing long enough to think, I realized I had come across something that I could really get into, and watch over and over.
As far as Excel herself goes, you either love or hate her (or both, as Ilpalazzo does). That voice could really grate on one's nerves, and most of the time she talks too fast to be understood. She also remains firmly set on the side of maniacal enthusiasm. Once past those things though, Excel becomes a symbol of spirit and loyalty. She endures Ilpalazzo's disdain, and even stands by him after he tries to kill her. She always follows her heart, which is guided by Ilpalazzo's will to take over the world. Add to that the fact that she's so dumb she can't help but be hilarious, and you've got a great character in an orange-haired, snaggle-toothed package.