I can check when I get home... I just upgraded (wiped the drive and did a clean install, actually) and I installed FCP X and FCP 7... but I rarely use either so I didn't think to open either of them after I re-installed them. I'd imagine FCP7 works fine... 10.10 is not a major overhaul from 10.9... you'll probably only really start to see problems when Apple changes file systems or stops supporting 32bit apps.