Dude - yeah, I see what you're saying, I guess it was a high-end diesel one or something, if it was the bog standard 2.0 petrol then I reckon I would've sailed past, the X3 weighs about twice as much as the ST!
This morning, same slip road, same situation, but I had a Caterham Seven in front of me. I didn't even bother...

That said, last night coming back from the gym I came up to a set of traffic lights, red, which lead into a 60 zone. Prime opportunity to try an (almost) legal 0-60 sprint. Revved it up and dumped the clutch at about 4k revs, little bit of wheelspin but I was away. It wasn't the most technical, or accurate test, but I'd not counted far past 7 before I hit 60. Very impressive, I was most amazed by the grip (I don't have ESP) when you're sending that much power through the front wheels.
Dealer - mine's not even open Saturday! Its a pain because I work 9-5 Mon-Fri so its difficult to get up there. Might have to go elsewhere.