The DFA 28-105 is the lens that keeps my camera functional. And, in reference to what Adam says about modern glass, I shot yesterday with the Rokinon 14 2.8 and the FA-J 18-35 and 28-105 yesterday,
The DFA 28-105 images just jump off the screen at you. Tess can pick them out looking over my shoulder. They have a 3D pop other images don't have. I'm not sure any "made for the way people take pictures" lens matches any "modern lenses for modern sensors" in anything except portraiture. I don't own any of the 3 amigos so maybe those lenses are better than I think, but I have seen many images.
I'm in a position now where I won't take the 28-105 off the camera for a prime, unless I need low light performance or reach.. My FA 50, FA 50 macro, 100 macro, DA 35, 40 XS have all become specialty lenses, although the 40 XS is darn good. But it's also right in the 28-105's sweet spot.
The DFA 28-105, everything jumps off the computer screen at you.