you push it in towards the nose of the car to set it, then up and down for faster/slower. I thought mine didn't work either, but realized I didn't know how to use it. It sucks anyways, it's not smooth at all. If I set mine at 65, it will speed up to about 68, then totally back off the gas (so you get that thrown forward feeling), and then turn back on at about 63/64. It sucks.
E36 Cruise is much nicer.
'86 325es (TURTL3): PJ peetsa hawler
'87 535is (BADWATER): almost done... really.
'86 325e (GRN HLL): DD/show/rocket
'04 x3 3.0i: Wife's Bimmer (manual, woot!) My BMW Blog