If you make Time Machine backups of the machine and it gets hosed during an upgrade to 10.8, you can always roll back, can't you?
I've never had the need to do this... yet.
The only problem I experienced after upgrading to 10.7 was that Citrix Access Gateway software was running at 99% CPU and killing my battery in a very short timeframe. Once that issue was resolved, I had an increase in battery life.
H