[popo]

This one seemed to me the way to go until I saw the picture: Why this protruding front element ??? We need polarizers at 20mm, plus thr protruding front element on the Signa 14mm f2.8 created me tremedeous  problems, disppointed...

Polarisers at such wide angles? Even at 24mm there is usually a very obvious sky gradient effect when used outdoors, unless there are other applications where this isn't a problem? 
 

The MTF is at f1.4. So, pretty good, considering. It will no doubt perform pretty well closed down a bit. Heavy beast, though.

Suppose the question is, how good is it compared to its nearest rivals? Not something that shows up on MTF, but I'm more interested in their claim of low coma far above absolute resolution (night usage).

Anyone know how to correctly convert the illumination chart to stops? Is it a 2x or sqrt(2) factor per stop?

"Great lens but soft at f1.8" - well, to me it killed any appeal of this lens; what's the point in having a f/1.8 lens if you have to use it at f/4 or so...

Generally a stopped down lens will be better than a wide open one. So using a f/4 lens at f/4 will generally not be as good as a f/1.8 lens at f/4. Of course it varies with the specific lenses you compare, and the values may be different.