funny you mention it as I'm selling my F11 520d, reason being I dont need a large car and my commute won't be 178 miles twice a week. I have not had teh 530d so can not comment, but have had a 320d, 328I and a A4 3.0 Tdi so i'm familiar with decent tourings.
All the horror stories about chains are only reported by those who have snags, which is the minority. The car I purchased had the chain done by BMW Snows, the new chain has new oil guides. I also do oil changes every 6k, the car system will prompt every 20k or so, which I believe is the main culprit for this failing. My (Arm chair) advice would be buy a 2.0 with the chain done or get a 525 or 530.
Other things that I have encountered are rear suspension air bags, engine bulkhead grommet leak, door card leaks. I find it a large car to park ( I live in Devon) but its a great place to be, we drove just over 2k at XMAS all round europe and on the autobhan, absolutely great. A 530d would have been even more fun. But the 520d was plenty.
Space wise I have gotten 3 kit bags, my road bike and a TV all in and drove to work in confort, wood to build decking, our new 65 TV went straight in, as did all the bathroom stuff from Ikea. It really is a step up from a 3 series, in terms of kit. M sport all the way!
I get about 650 to 740 per tank, but I drive mixed roads. If you set cruise or limit to 70 you will get loads out of the tank, again 520d experience only.
I'd see what the 535d and 530d owners experiences are.