[Revok]

Configuration used:

OSX Mavericks 10.9.1
Macbook Pro Retina 13"
2.4 GHz Intel Core i5
8 GB 1600 MHz DDR3

Fast Track Ultra 8r - Driver 2.3

Tested with
Quicktime
VLC Player
iTunes
Ableton Live Suite 9.1 trial
Logic Pro X 10.0.4

There are no problems installing or uninstalling the driver, and the control panel works fine.
There are no problems during playback in VLC, Quicktime or iTunes.
The problems occur when recording or monitoring audio from the FT Ultra's inputs in either Logic or Ableton. Frequent drop-outs or crackling and popping sounds. Adjusting buffer size in either software doesn't remedy anything.

So the problems apparently aren't limited to Intel Core 2 Duo configurations.

By the way: Avid's suggestion to "roll back" to 10.9.0 is ridiculous. Unless you happen to have a time machine copy of your full system at 10.9.0 (which I don't), there's no way to downgrade without a clean install/restore.