That's an interesting read from 2001. WAAS was released for general aviation use in 2003, and the WAAS LPV approaches I've seen, where the vertical guidance is derived solely from the WAAS GPS signal, have DA's around 200 feet. Some LPV approaches have (slightly) lower minimums than ILS approaches for the same runway. So while I'm not planning to stake my life on a portable WAAS GPS, I don't mind letting one alert me to a boneheaded mistake I'm making.