Spike: I struggle with exactly the same problem with the pebbly finish. It's very frustrating, as one session my Paasche Talon behaves beautifully and gives me the smooth, even finish I'm after. The next, it spits unevenly and often gives me that pebbly, dusty surface. I break the brush down and clean it after every single use and periodically run it through an ultrasonic cleaner.
I do wonder if weather conditions have something to do with it, as well, but I haven't been able to make a reliable correlation. Yesterday, for example, the weather outside was sunny and in the low 60s, no humidity, yet the MM enamel I was spraying dusted quite a bit, and I'll need to do some light sanding before moving on. Drives me nuts.
I also spray in a basement that's cold in the fall and winter and humid in the summer and dusty all the time, but I'd guess many guys here deal with the same situation.
At any rate, I'm also ready to try a second airbrush, perhaps dedicating one to acrylics and one to enamel and lacquer. I was leaning toward an Iwata, and Doog's endorsement of the HP-CS sealed the deal for me, and I've put that one on my Christmas wish list.