I've still only done c500 miles on my Diavel, and each time I take it out I learn more about the bike. I am nowhere near being able to use the bike to its full capability, and I'm not sure the UK roads / weather would be suitable anyway. I don't think you get enough time / variety of conditions etc. on test rides of high end bikes to fully evaluate them however you ride, although I think that riders with more experience of a variety of bikes would be better placed to do so. Long story long, I'm an "A" - but my god I'm looking forward to post-" 1st service and running in" outings!!!!
A ish - I'd concentrate on finding out how it felt and handled and just it's general behaviour, obviously a little squirt to see how it pulls but I'd be respectful of the dealers request as it's not my bike. Whenever I've ridden other peoples bikes I've treated them with respect, plus there's the added incentive as stated of "if you bend it, you've bought it!"
I'd have to say A) for me, I'm quite sure that something like that is far and away better than I am, and unless I'd been given a month long demo with no restrictions I don't think I'd get near exploring its capabilities. If you're used to quicker/better handling machines then maybe you can explore its limits, but I couldn't.
