Thurs 4/09: We upgraded 4th-day-free Hoppers from Cheaptickets (owned by Orbitz) on our last day. Once you trade in the vouchers at the booth (or a DLR hotel front desk), the tickets you get are identical.
If you are buying Hoppers and not saying onsite, just use your Magic Morning at DL before upgrading. Then upgrade ASAP for the discount. I should have done it sooner, but never had a good time to hit the booth. My choice would be evening, as the booth lines were bad mid-day.
You might check Way.com also. Looks like same price (no Ebates though). But I have read Way.com are E-tickets and go straight to the gate. I would avoid the ticket booth routine (Cheaptickets/Orbitz/vouchers) without more savings.