Just picked up a mostly base M3 last week. Manual transmission, leather/cloth interior, no Nav, no tech package. I had an Audi S4 on order, and the BMW people basically sold me on the M3. I was hesitant, but after 350 miles, I am SO glad I went M3. The engine is absolutely silly. It just wants to go. And the rest of the car feels like it's carved out of a block of aluminum, just so solid. I'm still in break in period, but even adhering to the rules, this thing is amazing.
Engine, just amazing. Not too much below 3000 RPM, but I'm never there anyway. Of course the handling is basically perfect too, flat, neutral, confidence-inspiring. It's an M3!
I wouldn't complain about better fuel economy, but that's not exactly why I bought the car.