I got an M3 a little over a year ago & loved every minute of it. Recently, I traded it for one of the new E60 M5s. I thought I made a great deal. but I immediately knew I made a horrendous mistake after driving off the lot. The M5 is quick, but is nowhere near as fun or involving as the M3. It felt like what it is: a big, oafy family sedan with a powerful engine. I never thought I would be so disappointed. After 2 days of owning it, I returned it back to the dealership, took a hit & got my M3 back. Now I could not be happier. I'm just more comfortable with these smaller, quicker coupes. Only a new 911 Turbo could replace it (in my opinion).
Sexy design (very classic), stiff ride that lets you know how in-tune the handling is; LOUD when you redline the engine; interior is simple, yet effective (not like the hellish iDrive system of new BMWs).
This is a 6 year old design that is pretty outdated as far as speed and performance goes. That is to be expected, but it my only complaint. It can easily be remedied with an AA supercharger, which should hold you over until the next monster purchase.