Apart from navigation anything else?

I'm not sure if this is true with the 05 SL500, but for the 05 SL600 if you get the AMG sports package it includes paddle shifters. The 04 SL600 does not. The paddle shifters are a bit different then the ones on the AMG models (SL55, CL55, etc..). You can up or down shift with the same button by hitting either the inside or the outside of the button. The button is on both sides of the wheel so it accomodates either right or left handed people. I like it better than the AMG models that have left button down shift and right button up shift.