I had my 15k mile oil examined at blackstone and I remember the condition of the oil was not as bad as I had feared. Car had around 40k miles at the time and I drive pretty hard. Sounds crazy but probably could have gone another 3k based on the oil condition. I'll look for my report when I go home tonight.
Here are other member's oil analysis:
http://www.e90post.com/forums/showthread.php?t=532197
http://www.e90post.com/forums/showthread.php?t=631045
I've always wanted to have my oil examined after a track day to see if it is really necessary to change it right after like some of my friends insist.
When I called them to discuss my results they made 3 comments:
1. We are using synthetic which lasts longer as shown on tests
2. 3k intervals is a good mantra but with modern cars can be too early
3. Our N54 engine is very well designed.