I'd keep it and use it. Like SaltyDog said, you may decide you don't like it but since you've already got it at least give it a chance.
Take a look at this post ...
http://www.finescale.com/fsm/community/forum/topic.asp?TOPIC_ID=17643
MikeV posted a pic that was drawn with an Aztek. I've got two airbrushes that have a generally better reputation than the Aztek but I could never turn out a drawing like that with either one of them.