I also considered and test drove c63 amg, lexus isf, s4, ctsV. In addition i considered R8 v10 and Gallardo but decided they were simply too impractical for me (2 seats and no real trunk just doesn't work). None of these comparisons turned out to be bad cars but the e90 m3 was by far the most refined. The four doors are very useful and the extra 22lbs. does't seem noticeable. In fact, a e90 without a sunroof weighs less than a coupe with a sunroof.
I also considered waiting for for the new m5 (I bought mine last year) but the massive size and weight of the new m5 didn't appeal to me.