It was very nice indeed. Aside from the extra space in all directions, there is definitely a sense of a higher level of sophistication about the A6 over the A4. Despite the size of the car, it has a more agile feel to it - front-end turn-in especially is much better - so that you are never really that conscious of the bulk. I feared the 2.4V6 might be a bit overwhelmed, but because much of the A6 bodywork is aluminium, the extra weight difference is not that great. It's no fireball, sure, and the engine does have to work hard, but it really is so smooth and refined, I'll take it any time over a 2.0TDI. The 7-speed multitronic is a noticeable improvement too, plus it had paddle-shifts.
All of that said, we're not sure we are going to buy it just yet. We're going to wait a month, because we have some funds heading our way in October to reduce the mortgage, and we'll have a better idea of how much we can afford to spend. We might still end up buying this car if it's still for sale then, or maybe a different one depending on what is available at that time, but what this has told us is that our next car will definitely be an A6.