Apple released OS X 10.10.1 (Yosemite) yesterday and it seems to have shaved off the most annoying quirks of the initial release where the Finder at time was close to glacial for some operations and the Magic mouse was often very unresponsive.
I have not found any glitches in the viewers I have tested that can be attributed to the latest release, so both OpenSim and SecondLife users can safely upgrade.
I found a problem with the SecondLife viewer after Yosemite was released where the installer from an auto-update would leave a ghosted mounted disk image on the desktop and the only way to clear it was to relaunch the Finder. Linden Lab has confirmed the issue and is working on a fix. This bug might be present in third party viewers that is based on the same code, but I don’t think any of them has auto-update so it may never surface.