I realise this post is veeeery late, but here's my tuppence worth.
We have a 520d MSport Touring Manual (58 plate). We tow a Bailey pageant S7 Provence (1490Kg MTPLM).
Overall average whilst solo - 43mpg. We get around 50mpg on a longish run to the in-laws (100 miles each way, all motorway). We cover about 500 miles per week, mixture of the daily commute and weekend shopping etc give the 43mpg figure.
We get around 25 - 30 whilst towing, depending on the route. Long motorway runs see it nudging up to the magic 30 mark.
One thing to note however, it struggles on flat road at 60, in 6th gear. 5th gear is where most of the mileage is done!
That said, it'll accellerate from 45 - 60 in 5th going up a reasonable incline on the motorway, it's really that 6th is just too long for towing such a heavy van.
In terms of ride, handling, behaviour - it's nearly perfect. The stiffer sports suspension means that the car has less "give" when the van hits a pothole etc but most of the time it's excellent. I guess the stabiliser and ATC (std on the S7 Bailey) both play their part too...
I would personally recommend the car. It's very comfortable, huge and economical. it's relatively high kerb weight makes it a good match for all but the very large vans and being rear wheel drive it's both fun when solo, and better at 'wet' hill starts than a front wheel drive...
All very subjective I'm afraid, because I have one and I'm happy with it. We were looking at a 525D, but the power and economy figures compared with the 520d just didn't stack up for us - it's a company car and the 525d is quite a bit more expensive on our scheme.
HTH
Vince.