MarketBasket is great for most things but sometimes Shaws or S&S has better deals when there are sales. But on an ongoing basis M&B is great for
Bakery -- their in-bakery is great
canned goods
Frozen foods, especially their brand of frozen veggies. Frozen meats (i.e. chicken fingers, meatballs are also good)
Packaged cheese and meat. Their laughing cows (which I love) aew $1.99 a package vs. 3.19 in Shaws.
Bread -- they always seem to have some kind of bread on sale.
The are not good buys for soda. CVS and Shaws are always cheaper.
Their meat is good, I still find you can get better deals at other places.
Product is good, they sometimes have good deals.
And the do take coupons.