I`ve run a 520D M-Sport Touring as a company car for the last 6 years. We normally swap cars after 3 years, but TBH I couldn`t be bothered with the hassle of changing then, and I can`t be bothered changing now.
It does everything I want of it, has enough toys, can get a wiggle on if you need to, and has self-leveling rear suspension (as do all tourings) which is brilliant for towing.
We tow 1500 kgs without any issues, averaging about 27 mpg (would do 30+ if I eased off a little, but i don`t pay for my fuel....), and I average c.45mpg week in, week out. Again, 50+ is easily attainable solo if you so wish.
i`ve now got over 150K on the clock, the car has needed 2 sets of discs and 3 sets of pads on the front, 1 set of discs and 2 sets of pads on the rear. It`s a manual (my preference, but the auto is lovely) and is still on the original clutch. It`s had 2 rear suspension airbags (1 under warranty, the other with a 60% manufacturer contribution) and thats about it. I only lift the bonnet when I run out of washer fluid, it has never used any oil.
Find a decent independent for servicing (about every 18K miles) and it won`t cost a fortune (my last service was £480.00 for a full service, rear discs & pads including VAT).
Great seats, lovely steering, excellent sat nav & phone system (especially with the `professional` system which has a DVD player and 20GB hard-drive for your music). Good range (easy 600 miles on a tank solo, 700 if you are careful).
I`ll probably run it until it drops, as I haven`t really seen anything that makes me think " Wow, I`d really like one of those". Some things have moved on, but not enough to justify the cost or hassle for me..