Have to say Ibbz, writing mostly as a roadie, that in the last 5 years or so road bike design has influenced mtb design. Bitd it was the other way round, and I remember reading something in the late 90's that said that if mtb design had progressed at the rate of road bike design, we'd all still be riding rigid 10 speed bikes with horizontal top tubes.
It was only when I started seeing new mtbs in shops with curved tubes and tapered head tubes that it occurred to me that mtb designers might be slowly running out of ideas. This would tie in nicely with the fact that mtb sales are on the decline, while bikes in general are on the way up.
As this thread is about aesthetics I'm sure you wouldn't appreciate my modern, massively tubed carbon road bike, but one thing's for sure; unlike many modern mtbs that have unnecessary suspension, disc brakes, weight, complexity etc, road bikes are all about speed. Nothing that doesn't need to be there. Minimum weight, maximum power transfer. Function before form, and nothing either more or less
Regards
Marge