Although I've only used this for a short time, I find it very accurate and simple to use. While there are apps out there that do much more, this one is exactly what I needed -- track my miles, and make it easy to back up those files (via the email feature) to my computer. The fact that it is so simple to use means I'm much more likely to keep better track of my business miles.
I do have one suggestion, though. The current version does not have any means of differentiating between vehicles, a minor problem if you use more than one car or truck for your business. A work around is to simply add a number or letter code in the "purpose-destination" box that refers back to each vehicle, but it would be nice to have a drop down box that allows you to select a vehicle.