Some annoyances aside, ray tracing was working well enough for me in the previous Fusion 360, but in the beta preview I'm just getting image corruption [see enclosed].
Late 2010 MacBook Air (1.8GHz i7 w/ 4GB 1333 MHz DDR3 RAM Intel HD Graphics 3000 w/ 384 MB)
OS X 10.9.2 13C39 (though also present at least as early as the GM release of 10.9.1)