I use a lot of Vallejo paint, and agree with all the above. The airbrush ready range are just diluted versions if the model colour range. They are very nice paints but clogging the airbrush seems to be a bit more of an issue. People use water or their own thinner with flow improver and a whole load of other stuff and get great results. I like them because their colour range is great but you do need to get them really thin (or at least I do) to go through a fine nozzle but this means I can build up really thin transparent layers of paint which gives a nice finish.
These are all done with Vallejo