The ability to shift while standing still or climbing is a definite plus. I also like the fact that everything is sealed up and I don't have to worry about cleaning or adjusting derailleurs.
I think I'm going to go with the frame only. If I don't get a Rohloff I'd prefer an SRAM drivetrain and v-brakes over the Shimano and discs of the complete.
From what I've read an 18" sounds like the right size for me at 5'10".
I think the 18" would work great for you, too, boc. I'm 5'8" and you can see my monster stem stack, so....