[XutvJet]

The N55 in M235 is quite torquey, especially with the 8 speed automatic which is light years ahead of what you have now in your 330D. However, it won't match the initial low end grunt of a 3.0TD, but after 4,000rpms, the N55 will completely run away from the 3.0TD. There will be a lot more shifting in the M235 as well, but that's just the nature of gasoline vs diesel. Gas mileage won't be quite the same, but it won't be terrible. I get around 22mpg in mostly city driving and getting on it often and 28-30mpg on the highway. I have a 6MT which gets lower mpgs. The 8AT will probably get an extra couple of mpgs in both scenarios.

The chassis of the M235 will feel far more lively than the 330D, especially when you hustle it. In 5/10 or less driving, the M235 feels pretty good, though many note it's a bit soft and rolls a bit. However, when you really push the car, it really does come alive and everything starts coming together to make it a true street-focused sports car. It's small size and strong power make it far easier to put the car where you want it.

The M235 and the N55 have proven to be quite reliable by BMW standards, but buying one out of warranty and with 57K miles means you could be in for some maintenance and repairs quite soon. If you don't service your cars yourself, the costs could be somewhat high. Here's what you could be looking at to fix within the first 1 to 2 years of ownership, many of these things being quite simple for a DIYer but quite pricey at a shop (shop prices listed):

1) New front and rear rotors and pads ($2000)
2) Brake fluid and coolant flush ($400)
3) New water pump and t-stat ($1000)
4) Valve cover and oil filter gasket ($1500)
5) Coolant lines ($300)
6) Spark plugs ($500)
7) A coilpack or two ($400)
8) Accessory belt tensioner ($300)
9) A shock or two ($1000)
10) Worn bushings on a few front suspension components ($1000)