Most of the rz/rb lenses have exceptionally nice bokeh, very smooth. But I think one has to be careful about blanket statements, and generally speaking, a lens might show nice OOF transitions for near subjects and less nice transitions for far, and vice versa. So... the proof is in the pudding, as usual.
The winners, in my book, are the 65 (I have the rb version), the rz 110, the 127 (rb), the 150 SF (rb) and the 210 KL apo (rb). The 110 can indeed give some dreamy results. I don't know if I ever shoot the thing stopped down!
I don't have the 140 macro but overall my experience with macro lenses ...across the board from 35mm to LF... is that because they were intended for ~1:1 they will show optimal transitions there, and not necessarily under "normal" shooting conditions. I have gotten edgy results from several macro lenses when shooting non-macro subjects.
I don't know about the 50 uld, I never looked at it from a bokeh standpoint, when using it I was mostly concerned with getting the corners sharp. But generally I'd expect it to be en par with the 65, which gives nice, smooth bokeh. but neither the 50s nor the 65s are fast, so... whether bokeh is an issue will depend on your working distance. The 110 is so fast that you'll notice the bokeh right away at almost any working distance.