You might want to join the homequiltingsystems group at yahoo.groups.com. This is a large, active group of quilters using a wide variety of mid-arm and long-arm setups. The rule-of-thumb advice on that group is to allow yourself a year to research options and try out various machines at quilt shows, dealerships, etc.
A lot depends on your price range. Also, having a dealer close by where you can take lessons could sway a decision.