Foster City is a lovely. I never had a guest who didnt admired the city while visiting our house. Its a hidden jewel of bay area.
Lagoon are nice. The novelty of moonlit boat rides wears of pretty fast. Same for Kayaking. Foster city allows electric motors . Lots of parks. No place to built anything significant anymore as the last open acreage was taken for the mix housing development. No large shopping centers or malls so no out of the city traffic. City will forever retain its charm of a small city.
Weather is 10-20 degree cooler from South Bay. Its a great plus that is often not taken into factor. Slightly windy in evenings sometimes. Close to airport but not on the air traffic path (just a small part next to 92). Center of bay area with easy access to all parts (read traffic part below too). San Mateo is increasingly catching startups pushed out of SF so proximity to jobs.
Two significant problems though:
Schools: Super overcrowded schools at elementary and middle school level. FC has no high school and city kids go to two different high SM high schools. With the new elementary it would be 4 elementary feeding one already crowded middle school. It would get worse in future.
Traffic: Entering city from north or south during evening is a nightmare. 92 east traffic wraps all the three city entrances with solid 20 mins and longer at any entrance between 4:30 - 6:30 on weekdays.