I've been following SBAS for a little while from a personal interest in satellite tech and the work of some folks I know, and although not all that clear as yet, I'm told that the system we'll be getting is slightly different and much more advanced than the other GPS augmentation systems out there.
I note various articles are talking about it (a) making Baro-VNAV completely redundant and (b) offering better than 100mm accuracy on approach.