I have 23k miles on my 335d and so far no issues. Had some nailed tires but wheel/tire warranty took care of the pricey Michelin PS2's
I do not regret my choice of going D at all over the I. The torque is just there for you. I get ~30mpg in shitty houston traffic. Cruise on freeways normally around 75mph, but mostly city driving.
Not many issues reported with the 335d compared to 335i.
JBD has a chip for it and i may go that route in the future.
Wish the 335d came in coupe/convertible in US tho.
The only thing i gripe about sometimes is the interior space is not as big for the money paid. I wish it was roomier inside like the 5series or even a honda accord. Other than that, its the best car choice for a daily driver for me. Luxury, power, and efficient.