Only issues I've had with the paintjob I threw on my notch a couple of years ago is that the front started to flake off where I did a crappy prep job (my fault, not the paint's), mine has some pretty awful orange peel and visible roller tracks in some parts because I didn't know to thin the stuff out 50/50 when I did mine (first try with Rustoleum, before I'd read about anyone else doing the same), and it has started to oxidize a bit because I'm a lazy bum that hasn't gotten around to giving it a proper buff in wayyyy too long.
I plan on sanding it down, giving it one more proper coat, and then wet-sanding it a bit to smooth it out, when I've got the time to piddle with it.
As it's been pointed out, what's the use in whining that you can't paint over it, when nobody in their right mind should ever paint over multiple layers of old paint in the first place and expect wonderful results. I went with Rustoleum because:
1. I'm poor and can't even afford a Maaco paintjob;
2. My notch has 270k on it (about 255k at the time I did it, IIRC);
3. The body has more dents and dings in it than I'm ever going to wanna piddle with fixing, so why throw on a fancy paintjob;
4. It was my DD up until about six months ago, so any nice paintjob I'd put on there would only get sandblasted by highway debris, banged up and gouged by idiots in parking lots, and/or beat on by the elements;
5. Paint won't make it go fast.
I refined my process a bit when I did Frankenstang's Capri a couple of months ago after reading up on others' methods of doing the Rustoleum paintjob. Still not perfect, but loads better than my notch (which didn't turn out all that horrible, anyhow). We kinda sped through the work on that one because of time constraints, and because we knew we'd have to go back and do a lot of it over again in the future, anyway (especially the roof ... ugh).
After multiple coats and two Foxes' worth of painting, I still have half a gallon left. That $30 can has lasted me a lonnnnnnng time, already.