Formula is derived from cows milk, so when you do switch him to the regular bottled stuff, it should be much easier for him to make the transition.
From 1 year old to 2 years old, he should have full fat milk and then from 2 years old onwards, he should have semi-skimmed. Research has shown that kids who were given full fat milk on a regular basis after (around) their second birthday are far more likely to have problems with obesity in later life than those kids who's parents switched them to semi-skimmed at this point.
After 1 year old and before 2 years old, however, growth is still rapid and the calories in full-fat milk are needed to support this growth.
Cow's milk, given in food (added to sauces when cooking etc.) is fine from around 6 months, but babies who are given it as a drink before 12 months will be left without nutrients such as vitamin E and iron and will end up having too much protein, potassium and sodium.
It's just a matter of giving you baby/child what is needed to support growth at different stages.
Hope that helped