We have Costco in Britain now and I quite like it, but some things are frustrating
1) You can only buy things in bulk - I would like to try a frozen dish before having to buy a dozen of them.
2) I dread the checkouts as there can be a long wait, and the way they have to examine your cart before you leave to make sure you haven't stolen anything.
3) I hate the way you always spend a lot more than you intended to. The prices are without V.A.T. and you sometimes forget that almost everything is really 20% higher than the price-tag.
4) They sell clothes but have no changing rooms.
5) They don't provide carrier bags or boxes to hold all the smaller items and I always forget to bring my own.
6) Eating there. It's very popular and cheap, but it's a carb-fest, mainly baked potatoes and pizza. Give me some healthy options!
I see Americans in there sometimes, who are living in London, and they are cock-a-hoop to be able to buy the products they buy at home. The free samples don't attract crowds - maybe the US has yummier ones - or bigger ones? The checkout people aren't usually rude, either. But actually I like more things about Costco than I hate, otherwise I wouldn't keep going there!