Alison Gootee
A few things to look for in a wheeled upright:
Durable nylon fabric, like Cordura or ballistic (the fabric in bulletproof vests). Steer clear of polyester bags, which are less abrasion-resistant.
Wheels that are recessed into the bag. They're less likely to get knocked off when the bag is checked. Also, make sure the wheels and the feet are as close to the edges of the bag as possible, to keep it from tipping over.
At least two handles: one on the side, so you can carry the bag like a duffel, and one on the bottom, so you can easily lift it horizontally into an overhead compartment.