Guys, driving a 6 cylinder Diesel with MT is really _no_ fun (like someone already said)!
Furthermore, the 4 cylinder Diesels have a REALLY crappy transmission and the shifting is just horrible in comparison to (let's say) 135i. They're worlds apart and you can literally tell that BMW put in cheap transmission parts into their 4 cylinder models to save money.
All in all: Diesel MT is a no-go. The 6cyl are either not available or no fun to drive and the 4cyl have a crappy transmission (they're not too much fun to drive either).
I'd get the 8 Speed AT.