Just a quick clarification: The above is true for the 590, but not the 580. The 3GB 580 is, from what I’m seeing, an excellent bang-for-the-buck RT/GPU renderer right now.
Also, the 290.36 drivers are working excellently with the latest RT code, which actually is faster than ever, around 17% faster than the last RT release. Note that you need those 290.36 drivers.
-Alan