I have had the Surco Rack for about 6 months now and I love it. You need to purchase the roof rack adapters in order to attach the rack to the factory rails, but once you do, it is SOLID. I haven't retightened any bolts and grabbed the rack the other day to see if any wiggle room had developed and the XJ started moving along with the rack.
It does seem like it is made out of cheap aluminum, but it sure stands up to what it's made for. I went whitewater rafting with some friends this past weekend, and the XJ became the main shuttle vehicle. We strapped an 8 person raft (deflated, weighing about 200-250 lbs) and a 2 person kayak to the rack with your basic straps and it stayed in place and did not generate any noise on the ride back along the fire trail.
All in all a very good rack for your money. My advice though, don't buy the light mounting tabs, just get some angle iron and make them to the specifications you want. It's cheaper that way.