I've got a custom-built powder-coated frame... for the extra cost, and the benefits of having it, it is pretty much worth it. Just be aware if you ever have to get a part fixed (i.e welded) on it, the welder has to burn off some of the coating. We just had major issues with the builder of the frame not wanting to pay for a re-powdercoat after having to re-weld some joints that were breaking.
You'll probably get lots of compliments on a nice frame for a year or so, or at least until it gets beat up. You may get a little color rubbing off on the rubber at certain contact points. Be careful about major scratches and dings, too. Like Chip said, the coating may flake from a ding.
4 out of 3 people have trouble with fractions.