Here in the DC area, I sometimes use the GPS traffic information, but as David said, typically don't bail off onto other routes because they can't handle the volume of all the traffic also following their GPS traffic info. WTOP does a frequent, yet abbreviated traffic report that usually covers the Beltways and bridges in a prescribed order. It's almost like during commuting times they can just prerecord the traffic and play it back on the 8's. There have been many occasions where I've sat in miles of crawl on I-95, yet WTOP reported no delays.
WAZE crowd-sourced traffic is useful to see there is something ahead, but most times the information about delays or alternative routes are inaccurate. I recently sat in a five mile backup on I-95 in North Carolina where WAZE contributors were obviously goofing off, posting ridiculous comments about bodies all over the highway, zombie apocalypse, no police on site, etc.
The local NPR affiliate, WAMU used to have the most accurate and comprehensive traffic reports, but dropped them completely a year ago when they had a management change.
I tried using the SiriusXM traffic reports a few times, but it seemed like as time went on information wasn't updated frequently enough. It was always like listening to the local weather via NOAA Weather Radio. One needs to wait though all the other coastal reports, river levels, temperature history, blah-blah, before getting to the local forecast.