yeah I've heard this too, but i've had cats all my life as has my mother and grandmother all the cats have always and still do drink semi skimmed cows milk every day, my two are now 1 and 4 and are both purrrfectly healthy!
when we got our last kitten [ she is 4yrs old now] the vet advised us not to give milk, he said you cannot stop milk if you have a cat that is used to it because they wont like water, but if you start as you mean to go on give the kitten only water, apparently its much healthier and better for their kidneys.
No milk is an absolute no no. I know some people do, but is causes all kinds of stomache problems. Milk has large amounts of things that can cause all kinds of gut problems. You can buy pussy cat milk in any supermarket.