I have signed up through mypoints.com, and received the free gas card offer. Unfortunately, my membership kit came a couple days before I was going to cancel, so I didn't have time to return the postcard to receive the gas card. I have also received an email with a promo of 2 free movie tickets and a $20 dinner rebate voucher. Don't count on getting your kit in time to redeem the postcard.
I did figure out how to get your rebate on gift certificates - join in the middle or 7 - 10 days before the end of the month, and order your gift certificates right away. You will get a credit back to your credit card the first few days of the following month, before the 30 days is up.
Hope this helps,
Amy