Hi, Jon.
I used this lens before and it is definitely heavier than sigma 20mm f1.8
Red Hawk post a pic of desert plant using this lens not long ago in post a pic section.
See below (I hope yu do not mind posting your pic here, Redhawk). His pic here is a great shot but mine was not at all...
The images it produces are not too bad in terms of sharpness wide open (only referring to centre image not at corners), and vignets obviously unless stopping down to f2.8 at least. Colour rendition is great but the bokeh can be quite ugly ... In fact, I was not that impressed with this lens wide open most of the time, ending up using other primes instead.
Though I happened to like the bokeh in this image above
Cheers
RedHawk, are you putting up a review of this lens in equipment section?