I still think (some) diesels are absolutely untoucheable in terms of fun / mpg balance. For short town trips they are indeed unsuitable, but anything involving 50+mph an a moderate basis they are very good.
I average around 40mpg on my 335d a mixture of motorway and central London driving (albeit at quiet times) but still has enough power and torque to make you smile. That being said, it is probably the one the best real life diesels out there when remapped, the twin turbos give it an absolutely decent powerband and it will surprise many a wannabe performance cars. Sound wise I have absolutely nothing on a petrol equivalent, it's a bag of spanners when cold but under full chat it actually sounds reasonable - more like a wannabe v8 than fake 4 pot scream.
Reliability wise, there is a list of niggles - nothing that can't be sorted in a weekend with a bit of patience and £500 worth of parts of preventive maintenance. There's a huge diy community and they are common enough that there's no surprises out there. They will then go on forever, mine is at 120k and doesn't miss a beat.