i don't think this would qualify as thread jacking, but i've seen a few shots from the 50L that showed very nervous bokeh that was really a mess. so much so that photozone even pointed it out in their review. I'm not saying the 50L is a mess, i'm saying that even lenses known for their great ability can trip up sometimes. Most of the early samples i saw on the net of the sigma looked a bit nervous to me, but in my use, so far anyway i haven't seen a problem.
BTW- and this probably is thread jacking, most people love leica bokeh, and almost everything i've seen from them is clearly a bokeh disaster, so who knows? perhaps dropping that level of cash on something can cloud your vision. hey, i made a pun, hi five!
Yeah! *high five*
Even Leica glass has comma and nervousness that can make anyone wonder why all the cash for a few pieces of glass.
But as for me, I love nervous background bokeh, I want a crazy vortex of light and colors! But not always, it does get quite distracting.
Photozone is right, the 50L produces crazy bokeh in the corners, and I've come across several examples of that, nervous triangles tearing apart the rest of the smooth OOF background. I've seen tons of great example with the Sig 35, and like anything, you look for trouble and you'll find it, nit pick and try and find what doesn't look good and yeah, any lens will show a flaw/something dissatisfactory to someone.