The 720 is a good un, my bluetooth is fine with my n95 8gb, when on motorway, it is a bit hard hearing sometimes, but you link it to your car speakers which is meant to be much better, but you cant listen to the radio then tho. Battery is shite, but they all are, mine is plugged in 24/7 when using in the car. Simple to use, big screen, and updatable to the new 730 software which has lane management...
Have a look on www.avforums.com for reviews and stuff on it, you can pick the 520 up for little money now as the new versions are out.