I installed Rift on Crossover Mac 11.0 using the Crosstie file and got it running. I had the problem of crashing immediately after character creation, but that went away when I set my video settings to medium in the game and running it in windowed mode in Crossover (emulating the virtual desktop). All is running smoothly enough and I've got to level 5 without a hitch, although the game appeared to crash and submitted an error report when I exited.
This is on a 2008 Mac Pro running OS 10.6.8 with an ATI Radeon HD 5770 card installed.