Keith, you are close to London: go to Greys of Westminster and ask for a test shoot there and then. Since my local wholesaler abandoned Mallorca, I have bought from them by post and find them honest, professional and very fair. A few minutes shooting outside the door would answer all your questions by your own hand, the best test there ever is.
Rob
Rob, to be really sure I'd rent and make the comparison with what I already have. I used to use Greys but have an excellent Nikon dealer closer to home, avoids costly train fares or congestion charges and they offer a rental refund on purchases.
You mentioned elsewhere that I should listen carefully to V. At times I get somewhat frustrated when I miss focus when shooting wide apertures with manual focus Leica lenses but the qualities when the Gods are on my side more than compensate. I'm envious of V's auto focus, image stabilised capabilities and she's envious of the qualities of my Leica lenses.
The grass is always greener...