I have a love/hate relationship with the stuff. It sprays well, comes in a nice dropper bottle, has a nice color range, cleans easily (I use Windex with no problems) and does not smell bad.
It does however dry very quickly on the needle and, at least on certain colors, has a tendency to lift very easily even with low tack masking tape. Using their primer will help a little but it's still quite fragile and a careless, light touch of a fingernail will scratch it down to the primer.
Regarding their primer... think of it more like a sealer than a primer. Something you apply over your regular primer as a type of adhesive between the primer and immediately before final paint. It does not sand well and tends to roll up under sandpaper.
I never found a good sub for their airbrush thinner. It's good stuff.
Here's another comparison chart site:
scalemodeldb.com/.../vallejo