I am. I've switched over entirely from other TTS programs to Mac voices. Pretty neat trick I use to batch each file using terminal. It takes a little bit to set up my transcript input files, I haven't automated that part yet.
Basically, when the script is approved, I generate a .txt file for each bit of audio (on the plus side, I have found a way to use this as a transcript feeder). Then I setup a batch file for terminal to automatically generate the outputs. The batch template lines look something like this:
say -v lee -f /Users/sflowers/Desktop/Dropbox/projectname/production/scratch_audio_scenarios/s1_c1.txt -o /Users/sflowers/Desktop/Dropbox/projectname/production/scratch_audio_scenarios/s1_c1.aiff
Copying and pasting this line into terminal will grab the text file and output an audio file in the voice I've selected. Copying and pasting multiple lines will do it multiple times. It only fails if there's a funny character or the text file is missing. Easy to pick up by the file size of the output .aiff. All in all pretty fast. And really easy to update. Just update the .txt file and copy / paste the batch line into terminal.