The greatly-improved GPS position accuracy offered by WAAS (Wide Area Augmentation System) provides some large benefits. If you fly IFR, WAAS offers precision approaches to thousands of new runways. These runways do not handle the amount of traffic needed to justify an ILS approach. Some offered IFR approaches previously, but these were typically non-precision approaches with much high minimums. With WAAS, you can fly a precision approach, with greater safety, closer to your ultimate destination.
Additionally, WAAS precision fixes provide the basis for ADS-B traffic (Automatic Dependent Surveillance – Broadcast). We are now beginning to see remote WAAS add-on boxes that offer ADS-B compliance to legacy Transponder systems. They are a great idea, and allow you to be in compliance. However, this WAAS information is typically only available to the ADS-B Transceiver. If your budget and panel space permit you to mount a WAAS GPS Receiver in your panel, not only can you comply with ADS-B, but you can benefit by using WAAS for navigation and approaches.