I honestly haven't much of a clue, but I'm sure that a custom-chip approach like the Amiga's would still have its uses today. An entire computer system that has been designed so that every component works perfectly with every other component, no components have to resort to vague assumptions as to how others will act, and where the software has also been designed to make the most of the hardware, I'm sure, would reach a level of computing efficiency far beyond that, if at much higher cost.
I'm still amazed at just how much my A1200 can do with 2MB of RAM, a 14MHz processor, no active cooling (I hate massive CPU fansinks!), and an OS that fits in ~10MB of disk/ROM space. (And I can't wait to see what it can do with an accelerator board!) When you compare that to modern OSes that require about 100-1000 times those numbers (alright, they do much more than OS3, but not quite that much IMHO)... I'm sure that the Amiga's tight architecture was responsible in at least a small way for that.
