After running Pro Tools for 4 months now, there have never been issues with my two MR816 CSX with Pro Tools.
The few times I need to start Nuendo, there is 50/50 chances to run into some kind of trouble (lost my studio setup, can't find the MR's, drop outs etc).
Steinberg told me that the FireWire on my Mac caused the dop outs in a middle of a Nuendo session.
I never have these drop outs with Pro Tools, and I'm using the same MR units...
Why do I not run into trouble with Pro Tools?
Don't have a clue. And I could'nt care less...
It just works