One man's opinion...from 
http://www.honestjohn.co.uk/index.php?url=/carbycar/index.htmWhat's Good
Very compact. Snug cockpit. Doesn't buffet badly up to 80 mph. 140 bhp 1.9 auto available. 190 bhp 2.8 litre six replaced by new 231 bhp 3.0 litre six in Spring 2000. 321 bhp 3.2 litre 'M' version almost too powerful. American built. New small engine range from Spring 1999, with 115 bhp 1.9 litre 'four' and 150 bhp 2.0 litre 'six', then 170bhp 2.2 litre six. Improved unlimited mileage two year full manufacturer warranty followed by one year full dealer warranty from November 2001, making total three year unlimited mileage warranty. BMW, Toyota and Ford jointly suffered the fewest breakdowns attended by German ADAC during 2001. BMW had sixth lowest average cost in warranty claims for cars up to 10 years old in 2002 Warranty Direct index. For more info link to Sportscar Guides 
www.sportscarguides.com BMWs generally had below average warranty repair costs in 2003 Warranty Direct Reliability index (index 81.41 v/s lowest 31.93). Link:- 
www.reliabilityindex.co.uk 9th top car out of 137 in 2003 Top Gear survey.
What's Bad
115 bhp and 140 bhp 1.9 litre fours not really enough except for cruisers. No clever roof like the SLK. Not very sporty to drive. Soft-tops can leak. Optional hardtops offer poor seal for side windows - modification kit available from early 1999. Z3 'M' coupe may be fast but is aesthetically hideous. Pre-November 2001 3 year warranty required expensive top up to be comprehensive in 2nd and 3rd years.
What to Watch Out For
Build date from 2001 shown on engine compartment label on top of front nearside wheelarch. Many RHDs were personally imported to avoid long delivery dates and don't have UK 3-year dealer warranty. 2.8s imported from other markets may have vulnerable Nickasil-lined bores rather than steel-lined bores. Check fuel tank for damaged from bottoming out (very expensive to replace). Front suspension lower ball joints and inner bushes wear, but are comparatively cheap to replace. Service light indicator can easily be re-set, so a paid invoice is the only guarantee of a recent service. Check took kit is all there.