After upgrading to OS X 10.10 (Yosemite) I consistently had sluggish graphics performance for all applications, but this was particularly evident when running the Singularity, Replex and Cool VR viewer, and to a lesser extent the SecondLife viewer. In reality having shadows turned on made using the viewer close to intolearable with frame rates typically in the 5 fps range.
A good system reset seems to have cleared this issue for many, including me, where after the reset frame rates returned to the 25+ range with all shadows turned on.
The reset basically is a 3 step procedure where the machine is first booted into safe mode and permissions on the disk are verified and fixed. Then the System Management Controller (SMC) is reset, and finally the Parameter RAM (PRAM) is reset. There procedure is described in this Guide: How to solve Yosemite memory leaks and CPU usage artice on Apple Support Communities.