I've got one of the smaller Kelty Carports (w/o the side curtains). I bought mine NIB off Ebay so I don't pay anywhere near retail which is the only saving grace. Needless to say, I'm not overly impressed considering what Kelty wants for them. The corners where the poles attach are stressed pretty hard- numerous reports on-line of them failing at that point. I had a local upholstery shop sew some reinforcing patches into my corners. The other thing that bothers me is the window- the curtain part for it is inside so if it rains it's going to puddle then leak in. It's a very neat looking structure though.
I recently bought a canopy from Wal-Mart for $32 after one of the guys on thesamba.com recommended it for those on a budget.
http://www.walmart.com/catalog/product.do?product_id=10993394 It's no Kelty, but for the price it's perfectly suitable. It goes up easily with fiberglass poles in the canopy and metal poles for the legs, has guy lines to secure it (includes metal stakes), it's arched so it sheds rain and allows you stand up under it when attached to the vehicle (I just use two of the poles and attach it with magnets) and it can easily be used similarly to the Kelty- just don't use the legs. I'm planning on sewing a strip of nylon onto the side I attach to the bus and possibly some tie straps to give it greater versatility.