Some of the rebates are actually credited to an AMEX card that They send you.
So, you then use the card to pay for something else (or maybe cash in if it allows it). Presumably you would then cancel the credit card before the monthly fees for "being a member" kick in -- 6 months in the fine print I read online.
In my case, it was just a small reseller with a really low price, not a rebate.
The dye inks are really excellent. At least as good, if not better than local Noritsu RC paper prints and Bay Photo's laser prints on Kodak Endura or Fuji Pearl papers. ICC softproofing worked perfectly out of the box, and with three gray/black inks, the monochrome prints should be good as well.