Waze is effectivly a much better version of sat nav, i use it all the time as it indicates very close to the time of arrival and is very good with traffic estimation.
for example the tyne tunnel is 35 mins on a clear run, on a weekday morning when i put my work address in it pretty much tells me if its worth the journey, most days its about an hour at peak times. theres many ocaisions where ive just called workto say im working from home due to it predicting a 2 hour drive to do 35 mile
ohh and it tells you in advance about mobile speedcameras, i wouldn't use anything else for sat nav these days.