The app is fairly accurate. My wife and I have been using this since 2010. When you open the application, it can take a few seconds for the location to update.
What is not accurate is the notification for addresses. I've never gotten that to work right - even recently when I tried. It either refuses to notify or goes off when they aren't even there. Thought it was just me.
That said, the location feature itself is really accurate. So I just check manually when my wife gets near home or I'm curious if she left work etc... She does the same for me. Notifications have never worked well for us.