No one would hazard to write it will all work. Why not clone your HDD, try the clone drive? It's not as if we should be without a backup today. You would be devastated if your current setup vanished so a clone is best.
Bob
I have a lot of software installed through macports like python, OpenCV, etc. Will this remain intact after upgrading to Yosemite? I had heard a few complaints form people who had upgraded to Maverciks last year that a lot of their software got screwed up.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic