I had an E90 M3, and it was a really nice car, but was very expensive to keep going. It would nickel-and-dime you with random electrical sensors going out, except the nickels and dimes were $500 and $1,000. Replacing the battery cost about $600 because besides the part itself being expensive, it had to be programmed to the car, I think to reset some kind of adjustable charging mechanism. The manual transmission was replaced, that was under warranty, but would have been seven or eight thousand dollars otherwise.
The car had a magnificent V-8 engine, 8400 RPM and 414 horsepower, but that engine it was also potentially its most expensive Achilles heel. It had the rod bearing issue mentioned before, and if they weren't proactively replaced I believe could cause an engine failure. An engine for the car was over $30,000 if I remember correctly. The car also got 11 to 14 miles per gallon and routine driving.
The problem for me in having a car that goes 0 to 100 in about 10 seconds is that you want to go zero to a hundred in about 10 seconds. I decided some point I didn't want to risk that ticket anymore, so then I couldn't really use the engine except in short unsatisfying bursts.
I ended up replacing the car with this car, which I like better in every way except the engine. The great thing about this car is that you can use its primary asset, the nimble quick handling, all the time without going to jail.