The transissions are fine, clutches will go out, quickly if you ride the clutch, or don't give it enough time to fully engage before standing on the gas and releasing the full mountain of torque. The previous owner of my '03 was hamfisted, so the clutch was replaced at 34K miles, and the transmission at 40K (I got it at 37K, and noticed slight difficulty selecting 2nd). Haven't had any issues with either since then ('06). General prevent maintenance will be move than a 540, but it's a joy to drive.
The Beast: E39 Dinan M5
Beast 2.0: E92 M3
Lil Brother: E86 M Coupe (Gone)
"Control, Vision, Determination" These are the three fundamental components of the new generation race car driver!! SPEED is a by-product! -Memphis Raines