Layout's better, display is nicer, there's more I/O, and more horsepower under the hood which allows for some incremental sound improvements and more room for expansion into more/better amps, cabs and sfx. But, it's not a revolutionary product like the original and its siblings were. I think anyone who already has an AxeFx can afford to wait for some mad money to show up.
Along those same lines, those who don't have an AxeFx can take advantage of the dumping that will occur when the early adopters start selling off their existing units to finance the upgrade.