I don't actually know the history of r/d designs but for it to be used on virtually all modern bows to some degree or other there must be something in it!
I agree that as with any design it is all in the tillering, set in the inner limbs is a big no no. The 'mantra' in the TBB's of no set inner limb, a little mid limb and a little more out to the tips holds true. I don't look at the bend of a limb much anymore, or at least not as much as I used to, I have more faith in a good taper and keeping a very close eye on any set and where it is.
I just don't like a lot of reflex in a bow now feeling that if you have to lose 2 inches to get it to full draw you have probably started down the slippery slope of diminishing returns. Saying that some reflexed bows have taken a fair amount of set but still been fast.....many ways to skin a cat I suppose and there are few definite answers to all these variables.