The SMG works really well, its basically a manual gearbox with paddle shift and no clutch. A mate of mine had the same thing with an E46 M3. Was adamant he wanted a manual, but has ended up with an SMG and its spot on. They dont kick down like auto's do, and you can drop a couple of gears quickly when you need to. Plus on the upside, they automatically blip the throttle on downshifts. I guarantee if you drive an M5, be it an E39 or an E60, you'll want one!! One of my biggest regrets was selling the M5. Its one of the few cars that the Mrs Liked!! Driveability on the SMG is fine. You can leave it in full auto, or use the paddles when you want to!