I will go along with the later lenses feeling almost like toys. However the earlier lenses were/are acknowledged as being softer in contrast but with B&W this is possibly a bonus. Shadows are not so likely to get blocked up or highlights burnt out. I use all AF lenses with my F6 and so far have managed to deal with the increased contrast by increasing exposure and reducing development.
When comparing my AF Nikon lenses with those of my Bronica ETRSi, I use the earlier 'E' Lenses wich have slightly lower contrast and the effect is just the same. This also seems to give better colour rendering with colour negative film, the colours being less saturated and more natural.