Good new, we have been testing handyPrint on OSX 10.10 Yosemite the day it was released and found no significant issues. Only minor ones we are in the process of fixing. We have also added a new feature in the process that will allow you to “clone” or “copy” a physical printer and advertise it under a new name. This way you will be able to easily create a “landscape” version of the printer with your customized configuration. You could also create a “photo paper” copy that would print borderless on 5×6 paper size. This open a lot of possibilities that are not available on iOS.
You can see above the actual option (I might change the name to “Clone printer…” instead of the actual “Create printer copy…”.
Let me know which one you prefer. In the screen capture above you can see the copy I made and renamed “OfficeJet Pro 8600 landscape”.
I configured it to print in landscape. Now I can quickly print in landscape when I need 
We will release the 10.10 compatible version as 5.0.8 for the standard version of handyPrint and as 5.0.5 for the PRO version.