anyone have any luck using iphone apps that utilise the gps device?
i can't get a lock on my location.

It should work ok. Are you not getting any GPS lock at all or is your location a few hundred metres out?

Google Maps data for China is a few hundred metres out and it varies by city.

You can download a free app called GPS Info which will give your exact longitude and lattitude and also tell you if you are receiving that info through cellular triangulation or through gps. It usually takes a few seconds and clear line of sight to the sky to switch from cellular to GPS.