I've been using an app called WAZE on my phone more an more. I love it!
Use a phone mount on my dash to hold it
crowd sourced data gives great traffic info, re-routes, etc....
extremely accurate travel times considering traffic
also users report police traps, road hazards, red light cameras, etc.... and it warns you.
voice commands
great where there are lots of users to report data, such as cities and interstates. Not so useful in the sticks....
and as previously mentioned, need cellular data service coverage (doesn't use a lot of your data plan, even with constant use)
I also agree that a dedicated GPS is still useful for long haul routes, but less and less so..... really only when cell coverage isn't great.