Well, I actually do own a Chase Stockback Mastercard, so I can vouch that it's indeed a very nice card.
What happens is that you're
guaranteed at least 1% back on EVERY purchase, starting from your first $1 spent. For more % back as they say on their website (up to 12% back), you
MUST go through the
http://www.stockback.com portal and purchase online. This is great if you do any or all of your shopping online because that's what this credit card was targeted for. (I've talked to CSR about this, and you
HAVE to go through the portal; I tried to maximize my savings by getting cashback from both ebates and stockback

, but it didn't work, unfortunately.

)
What's good about Stockback's cashback is that you can opt to leave it in a Money Market Fund (Merrill Lynch S&P 500 Index Fund) and gain interest to put it towards a house, car, anything you want. You can even put in more money if you want from any Bank account. (What a great idea, eh!? Why wait until the end of the year when all those other credit card companies send you your rebates to you when you can let the money
EARN INTEREST during that year?)
Of course, you can always take the money out as cash anytime you want.
Anyways, Chase's Stockback card has been great so far, and the web interface is pretty good, although you have to sign up twice (First, to access your CC info, Second, for Chase's "BillPay" management if you want to pay online..although you can pay other bills this way as well - phone, electricity, etc).