OP here! Some more thoughts on blender now that I've fucked about with it for a bit.
most interesting rendering engine available (Mitsuba) is not really production oriented, the render times are absurd and it's rare that a complex scene finishes without crashing, if you can get it to work you can create some really complex and beautiful phenomena though, also suffers from being CPU only
the most useful rendering engine is Lux, it's still pretty buggy/unstable from the PoV of someone used to iRay but using the latest dev version I was able to get this render in 4 hours without a crash which is actually respectably fast on my rig. I doubt I could coax iRay into converging that fast on a scene with participating media. I'm quite happy with it and excited to use something like Brenda to maybe run some animation renders on EC2.
cycles is good for me to poop on, shitty docs. doesn't respect physics