I can confirm that both my Manga Studio 5, and the Yiynova MSP19U tablet are working fine with OSX Yosemite (v10.10).
MS worked fine right off the bat after the upgrade. For the Yiynova, I had to reinstall the driver for it to register the second monitor, but worked fine after that.
Early 2011 iMac 27” i7
Manga Studio v5.0.4
UC Logic Pentablet driver v2.0.4