If you're bothered about running costs or you just want to pose then go for a small engined one, but if you want to actually have thrills from driving it then you need a 2.5, 3.0 or M. Depends what you want! Think of the 2.0 as a heavier MX-5, if you ask me.
My car is 3.0i, 03 (August), 59,8xx miles, comprehensive BMW warranty (transferable, expires end of November 2011), mot to Nov 11, tax to July 11.
In addition to usual 3.0i spec (e.g. xenons), it has:
falken 452 tyres (better than the runflats lots of cars are sold with), full BMW service history, original Z4M (style 224) upgraded alloys, uprated brake pads (Redstuff on fronts, Brembo on rears), uprated stereo (10 speaker one), gradient tinted windscreen, storage pack/nets, cruise control, K&N uprated filter, sound generator mod done, stubby aerial, heated/elec/memory seats, wind deflector, aftermarket bluetooth. Plus a couple more I've forgotten: basically most things available on an 03 model except nav.
I haven't thought about pricing yet as I'm not ready to sell - it won't be the cheapest 03 around though, because frankly it's better than most of them, with the history to show for it.