WAAS and EGNOS are both forms of SBAS (Satellite based augmentation system) and are fully compatible with each other. If you can receive one - you can receive the other. A lot of rubbish on this thread!
EGNOS has been fully live since 02 March 2011.
Officially (
http://www.gps.gov/technical/ps/2008...e-standard.pdf ):
Global Average Position Domain Accuracy
≤ 9 m 95% Horizontal Error
≤ 15 m 95% Vertical Error
Worst Site Position Domain Accuracy
≤ 17 m 95% Horizontal Error
≤ 37 m 95% Vertical Error
In most conditions, measured accuracy is better than this.
WAAS / EGNOS (or the other equally compatible equivalents) bring this down to 1.5m.
Without SBAS, vertical navigation (ie - glide slope) using a GPS signal would be dangerous, with SBAS, it is possible. Approaches which are using SBAS for vertical navigation are known as LPV approaches. There are a couple in the UK but more are due to roll out soon.
Probably worth a look at
http://www.pprune.org/tech-log/49968...es-europe.html
The ICAO agreed that there would be GPS based approaches to all instrument runway ends by 2016, using either SBAS or barometer based vertical navigation, so more and more are going to appear (see
EUROCONTROL - Implementing Approaches with Vertical guidance using EGNOS although that doc is from 2010)