I'm another believer in the roller job, having painted my BMW race car that way. Did it as a joke after reading about it on the interweb, and get endless giggles from people who look at it and can't believe that's how it was done.
I went with a higher dollar Inerlux boat paint, which doesn't require as much thinning (and thus as many coats). The no-buff finish is really glossy, and if you get the technique down you can achieve an almost glass-smooth finish that will fool just about everybody to think it came from a gun.
It is more labor intensive because of the multiple applications and sanding between (I did it more for adhesion than to smooth it out), but the lack of mess from spraying in my home garage was worth it, not to mention the savings in materials over 'real' auto paint. Just remember, it doesn't do anything for your prep quality; do a crappy prep job and it will look like crap! You can't hide bad prep no matter what path you take.