Same here, whilst am very tempted by the 50i and infact when I purchased our 35d I was also contemplating the 48i or X5M. I needed 7 seats so I had to give up the idea of the M very quickly. Then it was the V8 vs TT diesel. Loved the sound of the V8 but the diesel sounded quite good too from the inside. And the number of options I have added to the car, pricing was almost on par. It all came down to fuel consumption, whilst the cost of ful is not of great concern, it was the subconscious thought having to do our bit for the environment that made me do the switch.