I've had no problems with stability and the render speed is a great improvement. The only real complaint I have is that it seems to take significantly longer to clear a scene than in previous releases, and the interface reaction when manipulating dials or working in the view portal sometimes appears to be less responsive than what I've grown accustomed to.

 Another feature I appreciate is the ease of adding additional runtimes. A few mouse clicks and you're finished. Overall, this is an excellent initial release.