Been a while while while ago that i haven't give some news, so here is some.
I've spent my last days on Iray, got Daz 4.8 for a while but didn't had found enough time to invest on Iray.
My 1st impression ? Clearly the advantage is Iray has been created by Nvidia ... This will help a lot the engine to use your CGs (Nvidia) with efficiency.
Render time is also so so fast in comparison of Octane Render, which is fast.
Iray still a bit more hard on how to customize your mats (glossy, diffuse, mesh emitters, etc) i don't put my hand enough time also :).
Btw here's a "test" render (so far finished) i still have an issue on the eyes, i have to find what's wrong with eyes to make'em "neat" without noise.
Render time ~ 20-30 minutes.