David,
Something is goin on with that unit. It was originally release stating it have a TSO Certified WAAS Receiver in the box, though not a certified GPS antenna. Well, that also changed as it now looks to not have a TSO Certified WAAS receiver.
I have no doubt the ADS-600-EXP unit is great and functions great. NavWorx makes great products and we've never had any issues with thier devices that I know of. I know the $699 was an introductory price and it was going up to $799. They had some odd pricing, basically to get the unit was a basic antenna so that it works, it was priced over the $699 in the first place. I would like to have seen them include the basic antenna needed to operate for the package price. Keep up posted if you decide to get one.