I'm not sure... I thought I wanted a 35... then no... then I thought maybe i'll go to the 85 f/1.2, but that is a ton of money to spend on an occasional prime, and the 135 is really nice but the focal length would be redundant with my 70-200mm f/2.8L is mkii... the 50's are all soft wide open... so I don't know.
I want something that is a solid wide open, but not overly wide like the 35 (and I realize that isn't that wide, but coming from a crop, it is comparable to a 22mm on a crop and that is pretty wide for what I usually photograph), so maybe I'll just go cheap for a little while and get an 85mm f/1.8. $300 for some low light functionality... solid performer, but obviously not as good as its big brother.