We use the UK English Emily voice on our Garmin.
On our previous unit (Nuvi 750), when we ignored her advice, she would say, "recalculating" with what seemed like a tone of annoyance. The newest version on the 2555 no longer says it. I kind of miss the fun of bugging the hell out of her when I choose to go my own route.
I also discovered that most of the Garmin data is compatible across units. You can copy all of the voices and saved points from one unit to the other, by plugging them in to a computer with a USB cable and treating the device like a USB memory stick. Just drag the various bits to the same folder on the newer device, and try not to overwrite anything vital. It was handy to return to France and be able to look up the restaurants we liked from a previous trip.