I'm on my 2nd BajaRack. Both have been the one piece standard rack. Here's my take:
I put my first Bajarack on with a lightbar and 4 lights, but didn't wire it up immediately. About a month later, I got up on the rack and spent a couple hours wiring up the light harness. I put a piece of luann (yeah, its thin) plywood up there to help distribute the weight while i was on it. I'm about 220 lbs. Not light, but within design specs for the rack, especially while sitting still.
Fast forward a few weeks, I'm cleaning it off the roof of my FJ and notice that all the runners going across are slightly bent down... !!! Nothing else had been on the roof before or after me wiring up my lights, except when I was at Wheeltoberfest and I stood on it. However, the rack wasn't bent where I stood on it, but rather where I had laid on a couple weeks prior.
Needless to say I was a little miffed and surprised it could've bent that easily.
John Gjata and Sergio were great about warrantying the rack... I got a new one a couple weeks later. Overall I'm very pleased with the rack and the service that I've received, but I worry a little about putting items up there. Just my experience.