Perhaps you're confusing the Las Vegas Hilton with the Atlantic City property? The Las Vegas Hilton is definitely part of HHonors, I've earned points there as recently as September and booked an upcoming stay in January through their casino marketing dept., providing my HHonors number with no mention made of them not participating. Also able to make award reservations there for 2009.

(In response to earlier posts on the thread, I do remember hearing rumblings that they would not be a Hilton property after 12/31/08 but I'm not sure that ever came to pass, seems they would have announced it by now with that date less than two weeks away)