I have seen lots of references to McKinnon's, but never a thread solely about them, so thought I'd start one.
First, it appears that the Davis McKinnon's is not connect to the Danvers, Everett and Salem NH McKinnonses, which are connected to each other. The websites are different as are the graphics. The store quality is noticeably different as well. I used to live very near Davis Sq, and can't claim to have ever enjoyed the smell in McKinnons/Davis during the summer time. It's been three years since I went in, so maybe it's better, but whew.
I recently visited the Salem NH chain store, and was very impressed. Excellent meat prices and fabulous selection. They had a stack of Flat Iron Steaks (a perennial favorite with the Chowb and the pups) at least a dozen high, at a very reasonable $3.39/lb. I find Flat Iron very difficult to get anywhere but Hannaford's. (When I asked for it at Hilltop Butcher Shop, the two guys I talked to had never even heard of it!) I bought four chuck eye fillets for about $4/lb and they were excellent on the grill two nights later. The prepared/pre-marinated choices were vast as well, for those who roll that way. I bought some lemon-butter chix breast (we're packing and moving, so convenience wins this week) That was pretty tasty and successful, for $3ish a lb. I had no cooler with me, so I didn't try the fish market offerings, but they looked very appealing. Good variety, acceptable or better prices, and for crustacean fans they had a jumbo lobster tank with the 2.5+ pound monsters in it. I never see those in the regular grocery stores.
The groceries by and large were a bit over priced compared to MB or Hannaford, but not outrageously so--less than Butcher Boy, for instance, with a bit broader set of offerings. The deli meat selections were okay, but not great. Only one "Virginia" ham to choose from. They do carry both Luzianne and French Market brand chickory coffees, though, which is a bonus. Beer and wine prices were convenience store average. Twelve packs of beer ran in the $14 range, though there were one or two $11 specials.
On the whole, worth an occasional trip, with coolers and what not to carry largeish quantities back to the freezer.