This isn't unusual. From that PZ article: "I reckon that some of you may be a little shocked by this [bokeh] but to be honest this is not unusual. The Canon EF 100-400mm f/4.5-5.6 USM L IS and the Sigma AF 50-500mm f/4-6.3 EX HSM suffer from similar issues although maybe not this extreme (the highlights)."
I sold off the 70-300G and just got this lens in a trade for CZ 135 1.8 (yeah, call me crazy, but I don't really use CZ enough right now)... Man, this is one gorgeous lens... I actially love the silver finish And the zoom is going to be awesome for outdoor stuff... I'm also going to try and see how it works an indoor lens with HVL-F58...
I don't own a copy of the Canon 100-400 or the Nikon 200-400 (I wish!), but I do own the 70-400 that I use with the A850.
It's a very impressive lens, IQ-wise. I have no qualms shooting it wide open all the way to 400, though I normally try to stop down to f/8 at 400 for max sharpness.
CA is very, very well controlled. I've been at 100% on a file and really had to look to try to notice CA, many times I can't find it.
AF speed is decent - not blazing fast like a 300mm AF-S, but it's decent.
I have a few shots to show some IQ, though nothing spectacular yet:
Bokeh can be nervous in some shots, like the giraffe in the above thread, I typically don't mind, but others find it noticeable. MFD is pretty good, and you can pull off some excellent semi-macro shots with creamy backgrounds.
All hand-held, wish I had a monopod with me but did pretty good. The last shot on that page is almost a 100% crop of a blue bird at 1/60s, 400mm hand-held. Not bad, especially considering I pushed that shot about +1.5 EV.
I like the location of the focus hold buttons, and the lens doesn't look as gaudy in person as I thought it would.
This lens was one of the factors (among a few more) that swayed me to the sony setup over a similar D700 setup.
Tomorrow night I plan to frustrate myself by shooting some amateur football at a highschool stadium at night with the 850, the 70-400 and a flash I'll post some samples, assuming I get any keepers.
As for SSS - I'm still unsure about how much I like it or not. I tend to crop a lot on my birdy pictures (FF with only 400mm, go figure ), but I'm convinced SSS has ruined a few panning shots I was sure I had nailed. I'll have to experiment with it more.
Though I haven't seen any comparisons, I would have a hard time believing a 70-200 with 2xTC would match this for IQ -- I'd love to see a shootout, though.
I think the hard part would be finding someone that had both setups.
And the zoom is going to be awesome for outdoor stuff... I'm also going to try and see how it works an indoor lens with HVL-F58... 
), but I'm convinced SSS has ruined a few panning shots I was sure I had nailed. I'll have to experiment with it more.