10.3.9 to 10.4. what are the issues

i am at 10.3.9 and want to go to tiger. i have heard of some issues with qt loosing opacity but thats about it. a lot of the new programs do not work with jaguar.

q. will i have issues with older projects done in fcp4?

q. will eye loose any settings?

off topic slightly:
is kinemac worth the upgrade??