I bought a Revell Proffi one some years ago. I never really got into it, I think I was a bit mean with the cost of the propellant gas.
So this year I bought a compressor and two brushes in an offer on eBay for about £60....
I also bought a gallon of cheapo celulose thinners from car parts shop so I'm not stingy with cleaning.
I'm finding the two brushes in the kit a bit cheap compared to the Revell one.
So far I've mostly been sraying some old Dinky cars to practice on, seems more worth while than just painting card etc. Also done a Tamyia Spitfire which I quite pleased with.
My advice would be to get stuck in and have a go, It's one of those things that needs practice. One of the first things I found was not to hold the brush too far away from the subject or the paint dries before it lands and you get a rough finish.
Have a look at this for some info..
http://www.howtoairbrush.com/Frank