Just took it out into the yard to play around a little, just about to download and do some pp. I can't do any comparisons to the original Bigma since I never used it, but can give a very limited few thoughts.
1. It's a bit of a monster
2. That said, it's a COOL monster.
3. The zoom range is insane.
4. OS seems pretty good. Handheld several shots at 500mm at speeds of 250 and below. Will see how they turn out, but in camera zoomed in, looked pretty darn good. And keep in mind I am NOT great with keeping bulky lenses stable. I'm sure I gave the image stabilization a work out.
5. Bokeh appears to be really nice
Anyway, it's 60 degrees in Chicago. Went to the nature center earlier today (before the lens got here). Tomorrow its going to snow, LOL. If the weather isn't too bad I might try to go to the skokie lagoons, or at least the nature center.