I have been using Igo Primo for quiet some time now, not only on the gps itself but also on the Iphone 4. now that i am not using the iphone I will put it on the Galaxy 3.
I have found the software to be top notch and very customizable when it come to skins which add capabilities. For what I do with LDriding it is the ants pants

There are a number of websites that you can visit to see what you can do with it.
All phones once you start using the GPS and bluetooth will drain power reasonably quickly, Whizz's idea of power is the way to go as is a waterproof case.