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There are pros/cons of every year/model. The new 5 series has been very controversial in styling changes. A used CPO 2003 would save some money and be a very good car. You could easily get a 530 then.
Consumer Reports has very good historical info.
If you can afford the 2005 530, there's an upgraded motor that's supposed to be out in the middle of next year that I've heard that's worth waiting for.
The new 5 series has had many 1st year glitches, some severe. Most revolve around software. Those probs. should be solved. The bigger issue is the poor BMW after sale service.
2004 E60 530is, Delivered 12/12/03, TiSilver/LGrey, PP, SP,PS, PDC, ACC, FRS, Step, Xenons, clear bra, body colored rear inserts. (Retired, 1983 henna red 320is)
2004 Corvette Z06 Commemorative Edition