There are as many different long arm machines as regular sewing machines. Figure out your wants and needs. Take your time, and test drive as many as you can.
I would really suggest that you join the yahoo group - homequiltingsystems. There is a wealth of information on that list. There are many files to read and check out. I think there is even a shopping list of things to look for, or options that are out there.
Just remember - when you do get one - There is a learning curve.