I have it on my phone, it's bundled with the package I get through work.
It is good overall. Fast, accurate, has real time traffic and a constantly upgraded database.
Cons are the small screen size of the phone and tieing up your phone while you are navigating.
Unless you really need to have the convenience of having it on your person all the time you could buy a dedicated GPS unit after paying for 6-8 months of the service.
