Lots of interior room (though it is a big car), but it is a 4 seater for comfort, not a 5 seater.
The boot is huge so you can literally throw things in the back.
The split tailgate is wonderful. Why don't all estates have this?
The V8 is amazingly smooth, tractable (pulls from 1000rpm in 5th - yes I have a manual V8, rarity I know), and has power to spare. Hits 60 in 7.5 and goes on to 150mph (yes I've tried it).
Manual box is strong and positive - hey, it's a BMW.
Traction control a necessary evil when controlling a 1700kg car on huge tires if you're tired. But turn it off to have some fun and this car does not disappoint.
Arm rests, air con, excellent seats, perfect ventilation, dual sun roof, the list goes on. This car is luxury sports estate. It does it all.
One down side - thirst. I average 21.5mpg and get 23.5 on a long motorway stretch (sat at a constant 85mph or so).
BMW dealers friendly, courteous, efficient. I call them, a week later they take the car from my workplace, service it, clean it, and bring it back before I am ready to go home. What more could you ask for? And cheaper than Honda, Toyota, and Mercedes too!
Have decided not to buy an M5 - my next car will be a 540.