The Neo o-ring isn't quite the same as the Master. It's fully enclosed in the body, and the nozzle has metal to metal contact. So, it aligns well. I just have a knack of getting the one bad one in the bunch. Check out my Paasche VL review for an example. If you want an airbrush that does fine detail and puts out a whisper of paint, and you are careful how you handle it, the Neo is good choice. Spare parts are still kind of limited.
There are lots of good airbrushes for under $200. The Badger Velocity and Krome, the Iwata Eclipse, and the Harder & Steenbeck Infinity are all fine airbrushes. The Badger Patriot is a rugged general purpose brush and can do hair lines with the new super fine conversion kit. The Paasche Talon is very capable if you don't mind the big cup. I haven't tried a Grex gravity feed, but their Genesis XBi siphon is well built and sprays really nice. Just take some time, read some reviews and something will feel right to you. Stick with a major brand and you won't go far wrong.
I hope that helps a bit.
Don