Costco has some unique frozen foods I like, and good prices on some fresh meat, but #3 above meant it was rarely worth going for more than 2 or 3 items, and #1 & #2 above meant it would always be a much bigger hassle than 5 minutes at the normal grocery store.
Although I fully recognize that the above times are probably highly dependent on the setup & how busy my local Costco stores are. If I could get in and out of Costco as quickly as the grocery store (I drive by both on my commute home) I'd still have a Costco membership.