Curiously, the Tamron lens was reasonably priced via official Australian sources (I used Digital Camera Warehouse) and very dear from my normal Hong Kong retailer (DWI).
DWI don't stock the Tamron dock. In Australia, it is as dear as bloody poison - around the $180 mark. Out of the question at that price. But you can get one from B&H, including postage, for close to half that price.
Nevertheless, I don't plan to buy one. I only have the one Tamron lens, no particular plan to buy any other ones - the 85/1.8 was just about the last hole in my rather-too-extensive lens collection ... er ... except for a 400/4 DO II of course ... and ... er ... one or two other things - and it's no hardship to switch off the anti-vignette function for this particular lens-body combination.
Admitted, I haven't had the lens for very long - only the one soon-aborted session with it so far - but now that I know how to work around this issue, in all other respects it seems just fine. It's sharp, it focuses nicely, the IS seems to work well. That'll do me.
PS: Arthur, I see you have been promoted to blue ink. Would you be so kind (if policy allows this) as to change the thread title to something like "New Tamron is NO dud"? The lens seems pretty much blameless here and the headline seems rather unfair to it now.