My personal opinion is that the 1-Up racks are the way to go. You'll spend money on them, but they're bulletproof. I have a 2-bike rack and 2 single bike attachments so I can take however many I need. And each tray is up 15 degrees from the previous one so you can still go through some bumps without dragging the rack.
That being said, I have bounced the thing with three bikes all through the Utah deserts and the fire roads of Colorado. Never had an issue. The rack attachment is unique (an expanding ball bearing wedges into your hitch) and I've always used a short U-lock to lock the rack to my rig and it serves to keep the rack on if the ball loosens up.
I bought this after my exhaust melted one of my carbon mtn bike wheels when it was hanging from a Yakima rack.