I just had a chance to test one in a shop. Impressions :
1) very good lens overall (except the so-so build of course)
2) somewhat less LoCA than the 58/1.2, which is to me very important
3) probably quite good wide open, but in the absence of AF fine-tuning, there was significant front-focussing, so I am not quite sure. The 3D subjects, having at least one more or less thin zone in the focus plane, at least suggest this.
This was a daytime test, so not quite to the point.