I am a first time BMW owner, as I bought a 2003 330xi from my son. At this point I question my decision. My wife and I drove it home from Colorado, and immediately we had a problem with the water temperature gauge. It would quickly peg hot, then slowly drop back to normal. This happened every 2-10 miles, clear across Nebraska.
I stopped at a dealer, and they wanted to replace a sensor for $1550. They said there was no indication of damage or overheating, so I decided to press on toward home. They mentioned that they should upgrade the software as part of the diagnostic fee, so I agreed to that. Turns out, that seemed to fix the problem. (That's what others have found out also.)
Second issue; with 118k miles, the car developed a bad oil leak. I just finished putting the car back together after replacing the oil filter canister gasket between the oil filter housing and the block. Not a fun job. Will try it out tomorrow after changing the oil filter and topping it off. Hope I don't also have an oil pan gasket problem. My son never promised it would be trouble free.
I do like the car though!