Im updated to 10.8.1 and am continuing to have audio stuttering. This was lessened in 8.1, but is still present on both my 2010 and 2011 top of the line iMacs. Wasn't sure if anyone has found any work arounds for this. Audio is out by the 3.5 mm jack to external speakers, but also does it out of the built in speakers.
I've also noticed the iMac runs about 15 degrees hotter than under Lion. As a result, both iMac displays have now gotten a few stuck green subpixels on their displays. Not sure if it's related, but ML does seem to be running hotter and usage habits and room temperature haven't changed.
Lastly, I've noticed that my HP photosmart printer also has scanne issues under ML. Granted this is HP not updating their drivers, but it also appears that apple has changed a lot more than indicated under the good going from Lion.
Really getting tired of this shoddy software.
iMac, OS X Mountain Lion (10.8.1), 27" Mid 2011 3.4 Ghz 16Gigs Ram