We just moved to Texas from California and needed to tow a small Uhaul trailer with our X5. I shopped around a lot but decided a DIY install of the execuhitch was my best option. The directions are pretty limited, but if you browse around the forums for some of the write ups other guys have done you'll get through it with basic tools. Don't start the job without Red loctite though. The directions don't say it's required, but then they tell you to use it on the bumper bolts on reassembly. The X5 really towed like a dream. Plenty of power for the climbs on I40 east out of Cali, even with roughly 4000lbs on the back. It also had plenty of braking power, even without trailer brakes. I had a little Uhaul 5x8 loaded to the max, and I don't think I felt a single sway or push from the trailer. Here's a couple pics. I had the stock wheels back on for the 1400 mile drive.
And if you're not familiar with the execuhitch, watch this video. It's pretty awesome, and doesn't require any reprogramming. No one has any idea the car has a hitch when the receiver is out. Makes the $800 price tag a little more bearable.