I haven't seen enough of the 1.2 to make that determination. In Castleman's comparison, the 50/1 stopped down to f/1.4 is definately smoother, with softer edges than the 50/1.4 wide open. I don't think that the test image lends to pretty background blur so much as it illustrates the way the OOF disks are rendered.
I'm guessing that it will outperform the 50/1 in most respects.

