Don't know which engines had the nickasil problem and can't adequately describe it for you (cylinder linings reacting poorly to American gas or something) but it was a big problem and maybe that's the metallurgy problem mentioned in another response. Perhaps you should also find out whether there are plastic impellers on the water pump and research the timing belt/timing chain question. Later engines had a timing chain (my M50 engine has a chain, for instance), earlier ones (the M30 that the M50 replaced) used a rubber belt which, of course, breaks.

I've never driven one, but I'm told by other Bimmerheads who own 7s that they are amazingly nimble and "light" for cars as large as they are.

If my memory serves, Steve's is a late model 5-Series which he chose to drive as a test bed to understand their diagnostic systems. In my view, the late-model 5-series are absolutely gorgeous cars. I'm biased.

Good luck and good hunting.

__________________
David

His:
2003 Dodge Durango SLT
2002 BMW E39 530i Sport
1988 Mercedes 300TE
Hers:
2003 Chevrolet Suburban
1999 E430