I agree about Stamford being the busiest station between NHV and GCT. For one thing, there are more Metro North trains that terminate at Stamford than at New Haven, even during the week. There are people who might live east of Stamford and along the New Canaan Branch who don't mind driving to Stamford for more rail service, especially getting an express train. With the New Canaan Branch running hourly service outside of rush hour, and having to change trains at STM when heading off the New Canaan indicates that people don't mind getting into their cars and driving to Stamford for more options. During most times of the day on weekends, MNR has four trains an hour that head to the city with two of those trains starting out in Stamford.