Well, now that it's so close, I might give it a try. My previous warehouse experience has been with Sam's Club, and although it was quite CLOSE to where I used to work (10 minutes), it was the wrong direction, so I found myself using it very rarely. I had a $10 or $15 membership as part of a group from work.
This new Costco is right in our regular shopping area, though, not out of the way at all. I think I'll still mooch off of my roommate's card for a while to see if I think it'll be worthwhile.
I find that, for me, the better practice is to try to avoid going into stores. The less time I spend in them, the fewer things I actually need. Remarkable, no? I've noticed this phenomenon for years, when I go Christmas shopping. Suddenly, at the time of year I could least afford it, there were things I wanted to buy for myself. Lots of them. Attractive, appealing things, that I had no notion of wanting or needing until I got into the stores.
Better to shop online, armed with a specific list, at Christmas time. I might not get the very best prices, but I'll miss the "Oh! Look at THAT lovely _____" syndrome.
Anne