before starting a membership, you should browse the store, and see whats it got in stock, and its prices first...
getting a membership to there is like a commitment. you'll have to shop a lot of savings to get the membership value difference, as if you never paid for membership. Also note that they don't offer variety of software. Its what they sell on their website mostly, which are family games, from like EA and Microsoft, and Vivendi.
There are if I remember correctly, 4 types of membership. Basic, Executive, Platinum, and something else.
Basic starts at around $50 a year I think.