I have a vague memory of seeing a RotoDyne take off from Battersea Airport as a kid with my dad. I have a recall of it being noisy, but all aircraft were noisy in those days, it was part of the fun!
Seriously though, are the problems THAT insurmountable that no-one wants to revisit the concept? The advantages are obvious and engine design and aerodynamics are a lot further along than 60 years ago!
Those little Eland engines would hardly do for an APU these days, and with lightweight composites and maybe non-combusting tip-jets or better noise suppression, it would almost certainly be no more noisy than an Osprey and a great deal cheaper!
Or is a a question of "Been there. Done that. Didn't work. Next!"
Mac (just asking)