The answer to your questions are YES, they can be airbrushed, and YES, beautiful results can be achieved!
I've heard alot of horror stories about trying to airbrush these paints. But I've been using them almost daily for the last month and have determined that once you "understand" them, i.e. dilution ratios, properties and pressures, they work extremely well.
A few hints ... use Vallejo Model Color Thinner (No. 524). I mix at about a 2:3 ratio, paint-thinner, then I add a drop or two of distilled water to thin the paint even more, depending on how much paint I mixed. The Vallejo thinner has a milky appearance, and is not water-thin, hence the addition of a drop of DISTILLED water.
I shoot Model Colors through my Iwata at about 22psi and can get very fine and tight lines.
I've tried adding retarder and/or a few drops of varnish, but that just seems to upset the ratios so I don't use any additives anymore.
One advantage/drawback is the very quick drying time. But that usually means just a quick wipe of the needle with a water-soaked Q-tip on occasion to remedy that concern.
Hope this helps.