All great responses! It comes down to what kind of "good" you are looking for. Showroom quality will cost you a little more on the paint, if you are only looking for a little better than spray balms, then you can spend a little less on the paint. Its good to keep in mind what kind of riding you do as well. If you like to boondock the trees and are "rough" with the sled, consider that during paint selection and preparation.
Regardless of what kind of paint you use, prep is a key component. Good sanding on every curve and bump, get in all those corners. Get a good primer (etching primer or Bulldog - as stated), you can also use a "build-up" primer like Hysol to fill in small scratches etc., and make sure that everything is smooth, smooth smooth smooth smooth smooth before you spray it. The prep work is key in painting. The better the prep job, the better adhesion and better look you will have as the final product.
I knew a guy that had a rule of 50-25-25. 50% of job was prep, 25% was painting, and 25% was polishing. He used to paint race cars with a sponge roller and tremclad and you would think they were done in a drafted booth. Was pretty impressive.