bmw straight sixes are extremely reliable.

slow for the money... you can pick up a 95 m3 for ~ 12k. The performance category that the m3 will be the worst at is straight line performance and they are still capable of running a high 13 while trapping over 100MPH. There is a strong aftermarket for the cars (although it is not cheap to mod a BMW).

Best thing to do is go test drive one on a windy road. IMO they are one of the most well-rounded cars that you can buy. I am also one of the biggest advocates of BMW's that you will find so I am slightly biased.