As a second observation, I believe that we have just come out of a period where bicycle manufacturers were much more involved with MTB design than Road bike design. I suspect that the frame designers may have been letting knowledge gained in this design phase to leak over into the new generation of road frames. It may be that if you check, you will find that companies with a larger MTB base are more prone to compact road frames and more traditional road companies have stuck with more traditional road designs.

Now that CF is on its way to being the designers tool of choice all bets for future frame design are off. A designer using a cad system to design for flex direction and amplitude may well opt for custom tube angles.

As to whether or not the average rider will notice the difference..........read the reviews and posts here when people are comparison riding and you can tell that they notice. A pro may be able to articulate exactly what the difference is but you do the average rider a disservice if you think that they don't notice ride and stiffness differences. As BSLeVan points out, there are many more variations then just frame design but when comparing apples to apples frame design still matters.