i've tried sport and comfort mode on the VW Tourag and it's VERY noticeable... even when going straight over bumps... you can easily tell when it's on or off. I honestly drive my x5 quite hard... have even taken it on a track... and I can NOT tell the difference with sport button on or not....

are you all sure that it's not psychological to some extent.... have your friend push it and not tell you when he/she does... and see if you can really feel a difference.

even one of the BMW instructors at the performance center said he could not tell a difference.

I want to be sure it's really working....

i usually turn the button on above 50 mph or so and leave it off when going slower.... 'theoretically' that makes sense to me, as i want better handling at higher speeds and more comfort at lower ones.