My rMBP arrived yesterday and it so far works fine with my Alesis Multimix8 USB, Iomega HD and UC33e. I'm becoming more sure that class-compliant USB2.0 devices are likely to work in USB3.0 sockets, while devices with drivers seem to have issues.
I will say one thing though... the once-beautiful Live interface now looks really craggy and rough on a gorgeous retina display... roll on an Ableton update... But it is a fast machine.
