I bought mine SPO a year ago and it is still under warranty. I understand the big gripe on BMWs is cost of maintenance as they age. Since mine is newer and I haven't owned if for long, I can't comment on that. However, I read below that the sunroof makes noise? No such thing. The car is a joy to drive, it is relatively economical, it works well on regular 87 fuel, workmanship and materials are great quality, it hugs the road and loves to fly, and is very quiet and comfortable to drive. I'm not a big guy (5'8") so it is roomy enough for me. If you're big, you may want to opt for 5-series. I've driven it at just over 110 mph going from San Diego to Vegas and it sticks to the road like glue.
Driving a BMW is absolutely the most fun. You never get tired. the in-line engine makes for smooth accelaration and a feeling that no other car has. Auto transmission is cool and funky...Looks are great, too...
Long term reliability and cost of ownership is something I have heard becomes a problem. But I haven't experienced this myself.