Greetings Phil;
The Final Cut apps were indeed already installed on all of my machines and no I didn't make a clone of my HD before taking the plunge.
I certainly understand the wisdom of doing the clone but my upgrade experience with Apple (by the way, I've made my living with Apple products since 1989) has always been positive and to date I haven't had any upgrade issues.
I don't know your workflow situation, but I wouldn't do the upgrade in the midst of a project or during a busy time. Also on a side note I can't say that I saw any performace improvement in the FCP applications after the upgrade to Mountain Lion. Although Mountain Lion certainly has a large number of features and performance perks for other apps, as I said...I didn't see any performace boost for FCP. Just my experience.
Keep me posted! All the best to you...
Syd Rodocker
Apple iTunes U Administrator
Tennessee's Electronic Learning Center