I love this place. The yearly membership is well worth it. I make up the savings just in the price of their milk vs. Giant Eagle. They probably have the best price on tires as well.
Almost everything I've bought here has been of superior quality, long lasting, and at a better price than you would find elsewhere. I don't worry about comparison shopping because I know if Costco has the item, it will be quality.
There are only a few of each item - for example, only a few printers or digital cameras, or sweaters, but what they do have is usually fantastic. The food is good and reasonably priced. You do have to buy in bulk and it's a little hard for a 2-person household to do without being overwhelmed and eating the same thing for a few days. Still, it's delicious and a better deal than you'll find elsewhere.
It can get really crowded on weekends (although this is the time to get free product samples), so stick to a weeknight if you hate crowds and you'll be fine. The store is well lit, very clean, and has very friendly employees and plenty of parking. The only downside is that they don't take most credit cards (just debit and amex). Sometimes we visit just for the atmosphere!