I've never seen an optical formula of the new Rollei Sonnar, so I don't know if it's identical. However, it is a Sonnar, so it's likely close.
I like the 40mm length a lot. I think the Sonnar in general can be very crisp in a a gentle manner. That seems contradictory of baffling, even as I read what I just wrote. It doesn't seem to display ever little detail, which makes it nice for portraits, especially women. Ask a woman how she likes every facial flaw revealed in high def.
I also think that what makes the 40mm Sonnar stand out from the rest is the wider field of view.
At the moment, I'm shooting a Rollei 35 SE (sort of to confirm my dislike for the LED models). The week before, I shot with a Rollei 35 (Tessar version), and I want to compare the results of a couple of scenes that I shot with both.