I've been an eBates member for quite a while now. Their rebates were much better before the dot-bomb era. However, they can still be pretty good. DD14 uses ProActiv and I get a 7% rebate on my orders. Their also pretty good with rebates from a few other sites like Breck's and Spring Hill Gardens.
The rebate checks are cut quarterly and they must be for at least $5.01, not counting any sign up or referral bonuses. Purchases made during the 1st quarter will have a check issued on May 15, so you wait a pretty long time for that first check. If you do not have the minimum amount in your account for that check, the money rolls over into the next quarter. They are very good about sticking to their payment schedule and my check usually arrives within a few days of it being issued.
When you shop at a site thru a link at eBates, you are issued a "Tracking Ticket". This tracking number is your reference number for your transaction. If you don't make a purchase at the time that you visited that site, the Tracking Ticket just expires. If you make a purchase, you can follow up thru the eBates site to see whether and when it is credited to your account. If it doesn't get credited, you can use this tracking number in your correspondence with eBates.
The only thing I don't like about their site is that if you use ANY kind of coupon code other than one from their site, you WILL NOT get credited for your purchase. They're very strict about it.