I like the peace of mind that comes from having a shock-insulating case on longer trips. If you drop a phone without one it can just shatter, and that would suck when you're far from home. So more reasons than one to get a nice form-fitting protective case.
Yep, that's a nice feature. Last year I swear I practically rode through some people's front yard by following my iPhone Tomtom when I asked for winding roads.

It will add a lot of time to any route, potentially, though. But I'd rather ride a few hours extra through fun, interesting roads than sit on a straight, flat highway and be bored.