With my twins, no dairy crossed their lips until they were about a year old. I don't remember either of them drinking milk until they were older - maybe closer to 2. Neither ate much in the way of solids and it seemed silly to me to use up their non-breastmilk calories on something that didn't give them much in the way of nutrients beyond what my milk provided. Our Dr. at the time completely disagreed and told me when they were 2 that they should be drinking 24oz of cow's milk every day (that was about the time we switched drs)! And they nursed forever, so introducing cow's milk didn't seem to have an impact!
DD#2 (currently 13 mos) had sips of cow's milk several times. We're a lot less concerned with avoiding foods until a certain age this time around (honestly, I have to laugh at how rigid I was the first time - and I thought I was a fairly relaxed Mama!). She recently discovered Chai Tea as DS loves milk mixed with a small amount of decaf Chai, and screams for it now. I treat it like any other food - I don't want her filling up on one food source, so I won't give her endless amounts, but I don't worry it's going to replace my milk.
Offering ANY food or drink beyond breastmilk is weaning. That's the actual definition of weaning, even though us in the US tend to mean a complete end to nursing when we say "weaning". Giving cow's milk, IMO, doesn't make a child any more or less likely to wean completely than, say, orange juice or scrambled eggs. It's just another calorie source. For formula-fed babies, cow's milk is the usual progression from formula once their bodies are developed enough to handle the less processed milk. But some people never drink non-human milk, and are perfectly healthy. There's no reason to introduce it at all. If you replace nursings with cow's milk, then, sure, you're using it to encourage weaning (but you can do the same thing by offering a meal of solids - it's not the milk, it's using it as a replacement). If you offer it just like another food or drink, then it's probably not a big deal.
I really don't remember when I first introduced cow's milk. I know that I waited until DS was at least 12 months before introducing yogurt and cheese. DS still doesn't drink much cows milk, and that's his choice.
