Right now, everything seems to be running pretty smooth (Instead of doing a fresh install, I just upgraded my Crufty Lion install). . . and while I wait for my copy of David Pogue's New Missing Manual to show up at my door, I'm just gonna bang on it until it breaks.
Here's some neat tricks that I've found to jazz up your MLion Experience:
Open Notification Center with a Keyboard Shortcut in OS X Mountain Lion (from OSXDaily)
Notification Center keyboard shortcut
Mountain Lion 101: Notification Center in a hot corner (from TUAW)
I've been seeing this ping around the Blogowebz for the past day or so. . . it's kinda a no brainer, but still pretty neat. Also, a 2 finger swipe left from OFF the track pad will activate notification center, as well.
Customize OS X Mountain Lion’s Notification Center Background (From Lifehacker)
Install Java in OS X Mountain Lion(from OSXDaily)
Keep your Mac from sleeping in Mountain Lion (From Macworld)
Restore RSS Visualizer screen saver (From Macworld)
Also, looks like Candybar is free now. . . so check that out.
CandyBar, Mountain Lion, and Beyond
Panic's Candy Bar is now free, goes to Iconfactory (from TUAW)
Mac Tweaking Tool CandyBar Is Now Free, Updated for Mountain Lion (from Lifehacker)