The quote comes from the Intuit FAQ for Mac, which says basically that they're waiting for Leopard to reveal itself before they release their own software. Not a bad reason for delay, I guess, but I really wonder what extra features Inuit might include in their software that would require Leopard to work. Will QuickBooks really be using any of the Core Image stuff to beef up their presentations and spreadsheets? Doubtful, but it would be awesome if they did.
At any rate, Intuit says that if you need QuickBooks right now, there's always the 2007 version, and to stay tuned for everything else, including a release date for 2008.