I use Waze every morning to determine my route to work (30 miles). Waze provides me routes that no other App I've used has given me (I've used Sygic, OCN, Mapquest, AAA, Google Maps, and 1/2 a dozen more). I find the time estimates are pretty spot on. The best feature of Waze is its real time and will change your route should traffic patterns deteriorate enroute.
The bad is, since the 4.3 update on my Galaxy S3 with Verizon, Waze no longer is usable. The screen is 'jumpy'. Waze & Android blame each other apparently. Today I use waze to determine best route, then simply turn it off and hope traffic doesn't get worse as I'm driving.
On long trips Waze is great as well. Its a social network for driving. Police updates, closures, warning, all are real time in Waze. In fact, since Google bought Waze you might notice some traffic info on GM comes from Waze users.