Dunno, we fly GBAS approaches in Europe to CAT I limit with the availability of CAT III once certified. It is very precise indeed, no difference to ILS from a users standpoint. However that is ground augmented so of course you can get more precise position data than with pure GPS.
Sadly, those approaches are still flagged as being in a trial phase, however they work wonderfully so far and we had no glitches whatsoever.