It is a good rebate for the Rebel XT and they are also offering it on some lenses and a few other cameras. Just don't hold your breath waiting for Canon to send you your check, they are notoriously horrible for sending them out in any timely maner.
On the last rebate they claim to still be back logged due to the volume they recieved after Christmas. My 6-8 week wait is now going on well over 3 months and everytime I call them they say it should go out in the next week or two (this gets old after a while).
So if you don't mind waiting it is a good deal, just make good copies of everything.
BTW.... Dell was also running a 20% additional pricing on the Rebel XT which brought it down to the mid $600 range with a lens. Not sure if they have run out yet.
Mike