I've got the OEM MontBlanc's too. I wasn't sure if i was going to keep them or not but lots of dudes replied that they were fine so i kept them. They were right!
The things seem pretty bombproof (76.5kg capacity = 168lbs) and man, they are silent! I've driven with the sunroof all the way open on the freeway and it didn't seem any noisier, and i was listening for it!
The plastic locks are chintzy yes, but i don't leave them on unless i'm using them for something, so they are fine for me. They go on easily once you get the initial setup done. As far as attachments, i can't say as all i run are surfboard pads. Sounds like everything from Thule and Yak work, though.
