Probably not worth it, depending on what other options are near to you.
I bought a
membership when they did their periodic promotion that gives you a free chicken, some batteries, cheap tuna, and something like $20 off the membership fee.
If I were to pay full price for a membership, I would need a big family and would then get the executive membership since it pays a percentage back, and the extra fee is refundable if you don't make back the fee in savings.
My roommate has a membership, so I'm on his account.
Just go shopping once a year with someone that has an account. Stock up on ibuprofen and other common drugs, cleaning supplies, etc. Just about everything else is more expensive than buying elsewhere, especially electronics. Some things are cheaper though. They have some excellent WR toilets that were $80 and perform better than units that cost $350+ at other stores. Synthetic oil is usually cheaper. Sometimes local utility rebates make things like LED bulbs cheap there.
Costco fuel is the cheapest around, and they are now TopTier certified, so the detergent quality is on par with Chevron, Texaco, Shell, Arco, etc