I checked here:
http://maxbimmer.com/forums/showthread.php?t=132783
but didn't find anything to look out for on 2004 530i's. I'm going to take a look at 2 this week.
To those that own em, can I get your opinion? Ive searched on the web and found really good perceptions on maintenance and seeing as its now a 6 year old car. All the initial kinks should be worked out and the only thing I'll be looking into is - I would assume - regular maintenance (oil change, brakes etc...)