Arthur, Mate, I wish you'd stop mucking up my 'Long Lens Lust List'.
It originally only had the Tamron 150-600mm on it, well reviewed, and fairly well suited to my requirements, plus I had their 24-70mm f2.8 and the 70-200mm f2.8, both highly appreciated, and at about 1/2 the price, and offering around 95% of the IQ of the OEM offerings, to my mind, real bargains.
Then Nikon came up with their 200-500mm, and I added it to my list, with a leaning toward the Nikon, till Mongo's tell-all on his copy. Nikon really do need to smarten themselves up, with their recent history of technical problems with newly released high-end gear a real worry.
And now you Artie, yes you, you purveyor of all things wonderful with Sigma, and it's ground breaking technology with their puck/dock, have caused me to add another lens to my list. And I should add at this point that I'm not anti-Sigma, as possibly the sharpest lens I own is the Sigma 150mm f2.8 Macro, the pre OS version. Scary Sharp !
So now you have forced me to add the Sigma 150-600mm f5-6.3 DG OS HSM Sport, plus Dock, to the list, noticing that with each addition the price goes up dis-proportionally. Thank you, I hope.
Now I know that you should not expect 'cut your finger' sharp images at 600mm or longer, particularly in Oz with it's heat and shimmer, but this dock sounds like a damn good tool, particularly with it's ability to micro adjust your lens focus and do firmware updates.
I guess until I actually have 'the cash to splash' the 'Long Lens Lust List' is somewhat hypothetical, but geez Mate, please don't throw any more spanners into my wheel of wondering.