Am I alone in preferring separate modules for each function?

Well, no, in fact most people use separate drives, for your reasons, or simply for the fact that they already had a DVD or CD/RW drive and just wanted to add the other. I'm not one of those people.

For me it's a matter of cost... The price of a good DVD drive and a good CD/RW drive is more than that of a good combo drive. I have the extra 5.25" slot, but I prefer one drive that does it all. I have no need to rip and burn simultaneously or anything like that, I never really copy CD's or anything. I pretty much burn the occasional CD, watch DVD's, etc and haven't felt limited by only having one drive. Why have two if one of them is always going to be sitting idle?

But your arguments are all valid, just not for my needs.