That sounds like a better way to do it, I'm just saying that I've never found myself really waiting for map tiles unless the network connection itself was awful.
I'm sure less data would mean more data connections squeak into the usable column, but I'm rarely in those places, so it's just not high on my list.
The turn by turn, though, would be much more welcome. Though now that I think about it, turn by turn would increase my use dramatically and probably expose more poor network situations where the client-side rendering would make a difference.
I always seem to lose data connection just when I really need it with google maps on iOS. The whole data everywhere thing works great in big mostly flat low density cities like LA but it doesn't seem to work so well in London and barely works at all in mountainous rural areas. It would be great if the mapping data were stored on the phone.
The turn by turn, though, would be much more welcome. Though now that I think about it, turn by turn would increase my use dramatically and probably expose more poor network situations where the client-side rendering would make a difference.