I'm at 26k miles with my 184 sport-nav auto now. No issues whatsoever with the engine/dpf regeneration, etc. However, I had two of the 175 diesels prior to that and never had any issues with either of those, but I do drive ~25k miles/year. Car came with the adblue tank full, I refilled it at 13k miles (takes 10 litres) and it's currently showing at 45% remaining so the usage has dropped. No issues refilling, especially if you have the correct filler bottles that lock onto the neck of the tank. Just have to be careful not to overfill, apparently. It's also a bit messy if you get it wrong (and smells of pee). Dealers do not automatically top it up as it's not part of the standard service regime, but probably would if asked.
The amount remaining is constantly monitored by an ultrasonic sensor in the tank (which you can just hear near the boot when you shut the car down); it gives about 3000 miles warning before needing a refill.
Having the adblue system does remove one of the two tailpipes, sadly.
Alan
