Assisted GPS simply means you get Cell ID assistance from your network provider which may lock down your position within 10 seconds as opposed to normal triangulation which may take 30 secs to a few minutes. AFAIK all SE phones with GPS reciever allow you to switch off Assisted-GPS when you don't need it. If you have unlimited data plan, you won't have to pay for the Cell ID data charges your network sends to your phone. But the problem is if you're overseas, and if you have pre-loaded maps for navigation then the only thing you need is sattelite signal for GPS, but with A-GPS, some data charges will incur from the local network that's tied to your network meaning you'll have to pay for it in that foreign currency. That's the only time you'll be paying for A-GPS and it may cost a bomb. No biggie, hope this answers your long standing question