Costco is ok. They are very sililar to Sam's Club and I would say slightly better. They are HQ'd here and people like working for them. They are known to play hardball with small vendors, forcing them to absorb the cost of production for enormous orders for all their warehouses, then demanding they eat the stock if it doesn't move. That can be lethal to a little guy.
CostCo recently pushed thru a ballot initiative here in Washington that opened up the sale of spirits in non-state-run stores. The state was opposed to giving up its monopoly but were bought off by the inclusion of an additional tax to offset their loss of revenue. This additional tax is not printed on the price tag, giving the appearance of a real bargain on licquor. It just shows up at the register where it is obscured by the myriad of other items people usually are buying on a CostCo run.
More relevant to this board, Costco has a strict "no firearms" policy, open or concealed.