On our trip 8/16 - 23 the guides said that that the Grand will be used for 2008 and the Thunderbird for 2009. We had no problems with the Grand. It is located a short ride outside the Park, there is plenty opportunity to be at the Canyon both during the tour activities and during your free time (they run the bus back and forth like a shuttle a few times.)
Tammy
I'd be happy to answer any other questions about that hotel or any of the others - mostly because I want to keep talking about my trip!