I have just updated the page with an image of the Large Magellanic cloud (just 2.5 minutes exposure) and 350D:
http://www.pbase.com/terrylovejoy/300mmf28
I don't think this lens is in the same League as the non-IS Flourite Canon 300 2.8 but does a pretty good job at f3.5 (see images). Even a f3.5 it is still not as good as the Takahashi Epsilon at the corners (although at the centre I think the Sigma might be a touch sharper). Interestingly, the lens seems to work slightly better with my modified 300D. I'll try to reshoot the LMC tonight with that camera for a comparision.
Terry