In my tests, there were a couple of minor bugs here and there, but overall, Yosemite isn't on the same level of instability seen with the first releases of iOS 7 and iOS 8; it seems pretty solid and reliable. But you could wait a few weeks for the first bug-fix build, if you want to be sure.
I have always said that Apple devices work better when used in concert. Continuity pushes the interaction paradigm ever further than before. Once you see the level of awareness that is possible between your peripheral devices and your computer, everything else that can't do this will seem archaic. I would recommend Yosemite just for Handoff alone; consider everything else a bonus.
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