I've got one and love it. It doesn't sway around as much as others at speed (like the 591) and the bike sit's securely, lower on the roof.
Bit more of a hassle having to remove the wheel, and the 20mm adapter can bit of a bodge to set up initially (I had to file a small amount off the ends to fit my Revevaltions). Also you can't lock the bike to the roof if using the 20mm adapter. Otherwise it's great, especially for QR forks.
I'm getting another one I like it so much but this time it's the Pendle version as I need a 15mm through axle adapter.
edit – I've also had a bike fall out of a 591. My fault as I don't think I did the clamp up tight enough but equally not something that could have happened on the 561.