The A-GPS (Assisted GPS) relies on cell towers, I think. If that's the case, the device would have to fall back on regular GPS, thus taking longer to get a fix on your location.

I don't think they would have put in any arbitrary made-up restrictions. If they have, go kick their butt and tell them I told you to do it

(Edit: I should have refreshed before I answered. I thought no-one had replied yet...)