Maps Navigation is quite new, and still nominally beta, but it's surprisingly nice. There are some weaknesses, and some stupid oversights. (The most annoying being that, while I can use voice recognition to say "Call Jane" and it knows to look in my contact list, when I say "Navigate to Camelot", it doesn't: the navigate-to function just plain doesn't think to look in your contact list yet.) But in general it seems to work pretty well, even if the voice sounds much more harshly artificial (Droidish?) than that of Serena, our Garmin.
But the *really* neat feature, which I'd been praying it would have, is really good traffic integration. Those who have been paying attention have noticed that Google Maps now shows overlays of current traffic; this information gets incorporated into Google Maps Navigation in realtime. So not only does it show how long it will take to get to your destination (which Serena does), and not only does it try to take traffic into account with that (which Serena does very, very badly), it actually produces pretty accurate results. I have a nasty suspicion that it's getting this accuracy via a back-channel that uses the phone to report current driving speeds like the Dash GPS does, and that has all sorts of potential privacy risks, but the results are lovely.
Which leads me to my next-desired feature, posited here to help head off the inevitable patent.
I'm using Google Maps, right? And I'm using Google Calendar for my schedule, at least somewhat idly. And Google Calendar has a Location field. What would make me take Google Calendar *far* more seriously is if they put the pieces together. Calendar knows where I need to be, and when. The phone knows where I am. The Google cloud knows the routing and traffic. So it would be cool and useful if I could set an alarm in Google Calendar, which would buzz the phone *when I need to leave*.
There are lots of goodies that would be worth adding for extra credit. I should be able to add an explicit margin for parking and walking time, and I should have a slider that indicates my tolerance for being late. (Possibly on both the user and appointment levels.) Google should apply its algorithmic smarts to not only use the current traffic conditions, but also factor in historical information about the route to guess what the traffic will be like as I drive. (Taking into account that, while the Leverett connector may not be jammed *now*, there is a 75% chance that it will be by the time I get there.) The "where I am" functionality should pay attention, and not bother to buzz me if I'm already traveling the right way.
But even in a pretty basic form, this would be a remarkably useful feature -- in many cases, much more useful than the conventional hard-coded alarms that most calendar apps come with...