BobYIL
Well-known
I owned several ASPH lenses (21/2.8, 35/2, 35/1.4, 90/2APO and 135/3.4APO) and sold them all in favor of keeping the non-ASPH versions. If my primary interest in photography was achieving cutting-edge technical perfection at 100% magnification on a high-end monitor, I might have kept the ASPH lenses. But in practical photographic use I never met anyone, no matter how impressive their credentials were, who could tell from the best, professionally-done prints, which version lens had been used. That's all I need from a lens.
The sole exception is the 35/1.4. I owned one for all of a week. The performance at f/1.4 was much weaker than my pre-ASPH 50 Summilux, another old design. At f/2 it still lagged far behind my V.3 and V.4 35 Summicrons, and it flared quite badly (it was crystal-clear inside, no fogging).
I used all versions of 35 Summicrons. The one I am most impressed with is the 8-element (v.1), still keep it. The aspherical version I sold two weeks ago as I never preferred to use it over the v.1.