It depends on the place accepting the coupons. If it is an emailed coupon or barcode. You can use them as if they were on paper. I have virtually printed coupons, screen captured it, saved it to a JPG and emailed it to myself. It has worked at BestBuy, Circuit City and or local pizza shop. As long as they have the coupon code to punch in at the register it should be fine. Some merchants do require that they have physical copy of the coupon to close out registers. A few places in Boston actually use just email coupons through a special service on daily and weekly specials and the phone barcode is scanned, its pretty cool!
Steven Hughes
MVP - Windows Mobile Devices
BostonPocketPC