Well, it depends on what you plan on using it for. Are you going to try to paint model kits and weather props with it or are you going to use it to touch up your car?
Personally, I've been through the cheap brushes and I refuse to buy anything but Iwata ever again. But then again, I use mine for fine detail work on 1/6th scale model kits, etc. So, it depends on what you want to do with it and how often you plan on using it. Is it a one shot deal? Are you just going to buy it for one project and never touch it again, or is it a tool you see yourself using often?
Also, on the subject of air supplies for it, don't get sucked into the canned air crap. By the time you buy ten cans of air you could have bought a decent compressor. Or if you live and work with this airbrush in an area where you need to be quiet, get a CO2 tank instead. They're moisture free and silent, so no neighbors complain about the noise of the compressor.
There are a lot of good deals at Harbor Freight for cheap tools, but with airbrushes you usually get exactly what you pay for. Considering that it's only $5-$10 though, it's worth trying it out. Otherwise, I'd recommend BearAir or Dixie's Art Supply for great deals on Iwata brushes, if you want a brush that will basically become an extention of your arm and last you a lifetime of painting. I'd suggest an Eclipse, which I've never used, but I have had friends rave about it, but my personal brushes are both HPCs. You can almost sign a check with it if you're careful. Or you can get the top of the line detail brush and go for a Micron....I'm still drooling over it, but even at half price through Dixie's it's still $265 and it's their most expensive detail brush. PM me if you want to talk about it more.
Nickoli, generally speaking what Raygun said is right, what you pay for is what you get with airbrushes; however, I purchased this same brush off of E-bay over a year ago just because it was so cheap. I believe the brush you are talking about is the central mnumatic 1500. This brush is an exact copy of a Badger 150 if my memory seves correctly. This brush comes with a fine needle and head assembly so you really can't do a lot of coverage very easily with it, but I'm able to get better atomization out of it for weathering than I can with my Paashe VL. For a general use all around brush this may not be your best choice, but for details like smoke and shading, or painting smaller areas it does quite nicely, and for 20 bucks you can't really go wrong.
I got the Harbor Freight $20 special and regretted it. It's a copy of a Badger 150, but total crap. Took it apart to clean it after the second use and couldn't get it to go back together again no matter what I tried.
Spend a little extra money and get something worthwhile... !!