Just upgraded to Mountain Lion. It had a problem and the Apple store did a wipe and install. I restored all my data and apps by ethernet from Time Capsule. I had to find and reinstall Java. Things appear to work ok except launching Time Machine gets a warning "Unexpected error occurred (error code -6584)." I've not yet recovered an old document so cannot say if it works.
MacBook Pro 15 in (early 2011), Mac OS X (10.6.8), 250G, 500G, 1T Ext HDs; FCE HD 4.0.1; CS 5