Did ML Disable TRIM for you on your 3rd party SSD?
After I installed ML I opened the TRIM Enabler app and found that TRIM had been disabled after the Mountain Lion update.
Turning it back on was just a click of a button and a restart away. I verified that its working now in both the app and the system profiler.
So did TRIM become turned off for you too after ML? And if you haven't checked, you may want to do so to see if you need to re-enable it.
I'm new to SSD's so this is already a known occurrence with new OS installs then my bad.