It good to see Holmes and Watson as youngish characters. I think all the previous films/TV programmes have them as middle aged which I think was not accurate because in the books, they would have been quite young because neither were married.
Most men in the Victorian era married for the first time in their early twenties so it would be logical to deduce both Holmes and Watson would have been in their late Twenties when they meet for the first time since Watson was unmarried at the time.
Also, Watson had been to university and then the Army, saw action in Afghanistan and invalided out when he was still fairly junior. So he would have been 30 max I reckon.