Yes. I have just gone through two Apogee Ensembles and unfortunately I don't think they like Mountain Lion very much. I wish I could get a refund, but I went through 6 MONTHS of tech support before getting this replacement unit and it's still having issues on my two computers running ML.
The issue on both my computers is that Maestro 2 often will not recognize the Ensemble is connected. You have to turn it off and on and then restart the computer before it recognizes. As well, sound will sporadically drop out and the Ensemble needs to be restarted. Also, the Ensemble has on occasion crashed and holding down the power button for several seconds is the only way to get it to turn off and on again.