Okay, a little rabbit trailing here...
Regarding running Google Maps on trips, I too do it all the time.
For me the best feature, aside from "live dynamic" time till destination, is it constantly shows the local speed limit on the road you're on. That's a huge plus when you roll into a town and miss the posted speed limit.
Going up and down the HWY 395 to Tahoe all the time, the speed limit can be up to 70 MPH, then when you go through a towns like Lee Vining, Lone Pine and others along the route, the speed limit through those towns is 25 MPH and I see all the time tourists blasting through at 40 or 50 MPH, not aware of the actual posted speed. Albeit, I've traveled this road so many times I know it by heart, but on other treks, it's invaluable to know what the posted speed on the section of highway you're on. Heck, I've been on highways cruising along at 70 MPH doing what I think is 5 over the posted speed 65 MPH and realize the speed limit changed to 75 MPH!
... and I'm wondering why everyone is flying past me??