I have a Liquid Saffire 56 and it works fine with the Focusrite drivers version 3.4. (I have to turn the input gain all the way up for my mics to have enough gain, though. Never understood why. Mics are Rode NT1000 and Miktek CV4. The interface sounds good.)
I've always heard good things about the RME stuff. Never had an RME product, though.
I have a Native Instruments Audio Kontrol 1 USB audio interface (it's an old product) and it's working fine with the latest drivers supplied by Native Instruments under Mavericks (10.9.3). I use it for MIDI (in/out), as an interface for my guitar, and to drive Yamaha monitors.