My two girls LOVE goats milk. I raise and breed dairy goats, and raw milk is by far the biggest treat in this household. The dog and cats both get small servings almost every night.
The reason cats, dogs, lactose intolerant people can drink goats milk and not cows milk is the lactose. Unlike cow's milk, goat's milk does not contain agglutinin (lactose). It's completely different from cows milk is many other ways. Although it varies, depending on the breed of goat, they overall yield much higher butterfat and proteins than cows milk. They also contain a lot more "good bacteria", even after being pasteurized. Pasteurized milk, goat or cow, contains very very low amounts of good bacteria. Pasteurization is required by the USDA to sell milk that isn't for pet consumption. However, it kills off the very small amount of bad bacteria (granted the animal being milked is kept/milked in clean quarters) and the whole lot of good bacteria. "Ultra-pasteurization", which gives cow milk a three month shelf life, is extremely harmful in particular.
The "smell" that you're referring to, unless the product makers have added something else to the milk, probably means it came from a dairy with Toggenburgs. Toggenburgs (which I raise and breed) yield very high amounts of milk, however many people complain the milk smells and tastes "goaty". Even if mixed with other types of goats milk, the smell/taste makes itself known. Personally, I like the taste of Togg milk, although everybody is different. However, vinegar is not a normal smell attributed to goats milk, so it could be the green tea extract.
My personal suggestion is to incorporate raw goat's milk into your cat's diets. My dog (who gets the runs even if she has a strange treat) has never had any dietary issues with it, and I feel as though it helps their coats, eyes, energy levels, etc. Around the world, goat milk is prized because it is often attributed to being the "miracle food". I've heard of raw goat milk improving sickly people's vitality, goat milk soap helping people with eczema, and many other examples. However, instead of buying it from a company, see if there are any local farmers in your area? If you live in a city, this may be hard, but even in suburban areas people often have nigerian dwarf goats (they're like pygmies, only more refined looking, and used for dairy purposes) that they use as family milkers. Make sure to check out where the goats are living and being milked, and things you should make sure of are that they pre-wash the teats/udder (normally with a iodine/betadine and water solution) and that they post-dip the teats (normally with straight iodine/betadine, or there's a couple of spray-on solutions on the market). You can ask them if they filter too. I don't, and it never really makes a difference, or you could do it yourself with a coffee filter.
Another thing to consider is the breed of goat. If you want to put some weight on your cats, or give them a "sweet treat", go with nigerian dwarf milk. Depending on bloodlines, they typically overall have the highest butterfat percentage of any other breed. Next in butterfat would be nubians (floppy eared goats). Everything else is pretty much a level-playing field in terms of nutrition, just watch out for Toggenburg milk if you have picky kitties who you think won't like it!
A half-gallon around here costs about $7, but it varies geographically.