I'm from Long Island and Stony Brook is a nice area. Yeah most of Long Island is suburbia, strip malls, etc, but out east is beautiful (wineries, ferries, right on the water) and the beaches here are great. Plus there isn't really a shortage of things to do at night - there are tons of restaurants, bars/pubs/clubs, malls, movie theaters. If you have a car you can visit other nice towns (Port Jeff is fantastic in summer for example).
the LIRR can be a pain in the ass, but it does run regularly. You can get to/from NYC no problem. During the winter, the LIRR is notorious for experiencing issues - "equipment problems," delays....not going to lie, I'm not a fan of them at all BUT I love living on Long Island.