I own a mk7 transit.
Here are the main things you need to know.
1. They still rust. They were either built in Turkey, or in Southampton. The ones in Turkey had more rust proofing and are better built. If you want to find out where it was built go on the transit forum with a chassis number and they will tell you. Mine was built in Southampton, and has some rust, noting major, but annoying non the less.
2. The injection system and engined are completely different to the mk6. The fuel injection system is far superior. I regularly go on the transit forum and haven't read of a fuel pump going on the mk7, and the injector very rarely.
3. They are nice to drive as the engine is a lot more refined than the mk6, and they are nice and quiet in the cab.
4. The major problem with these engines is they regularly knock out a piston. This is caused by over fuelling and the piston over heating. It is a combination of over pressurisation in the common rail and the ECU putting to much fuel in. What happens is, the PRV (pressure release valve blows on the common rail, and then the engine cannot regulate the fuel input. You can tell if it has blown because The engine will hunt badly on tick over once the engine is warm.
Don't let this put you off because you can prevent this happening. If you get a transit, you need to replace the Pressure release valve on the end of the common rail (roughly £60) and the suction control valve on the fuel pump (roughly £80) both easy todo. Then take it to Fords and have a PCM update along with a pump pilot learn, and injector pilot learn and the PRV Counters reset.
This will prevent any future problems with the pistons
I did all this on my van when I got it myself, it sounds a lot, but if you are handy with a spanner, it's only a few nuts and bolts.