Everything I have bought at Costco has been top notch Doc. That being said I don't buy briskets or butts there except when I am making Buckboard bacon. The reason being is that Costco, in my area at least, does not carry packer briskets and the butts are all de-boned. Also, their ribs are Armour brand which are enhanced so there a pass for me as well.
The rib roast, chucks, and ribeyes are topshelf though. You can also get some nice salmon, chicken, shrimp, and scallops. I really like the Costco chain and there are some nice items and good buys in the stores.