Changed my engine and trans mounts yesterday - didn't have any specific symptoms, but wanted to refresh things a bit at 74,000 miles.
Turns out my trans mount was completely toast - had loads of play and the rubber was completely separated/torn. I had started to notice a tiny bit of "slop" in the drivetrain, but seeing as these mounts wear and fail gradually, I'm sure I had just grown accustomed to it over time. Engine mount was in better shape, but also starting to show signs of failing - it was starting to tear/separate on one side.
Installation wasn't bad at all - hardest part was gaining access to the trans mount and the body-side bolts. Was a bit sketchy supporting the engine by jacking up an edge of the oil pan for the motor mount, but it all went as planned. Took about 3 hours start to finish for both. Car feels great now - less vibration on startup and idle, and shifts feel smoother/crisper. Glad to have changed them.