My 2 cents :

I live in Singapore. While in Singapore, the GPS lock is really really fast. Some time last month, I traveled to the US. Since I knew I was going to be in MA and CA, I downloaded both of those maps onto my phone. In the US, GPS performance was really bad. It probably took about 5 mins to get a lock when I was in suburban Boston, and when I was in the Bay Area, I'm pretty sure I left maps on for longer than 5 mins and did not get a lock.

Another interesting thing I noticed when in the US :
My battery life was not as good as it is in Singapore. I suspect T-mobile's network isn't as good as the networks in Singapore, and the phone has to work hard to keep a reliable connection going. I was on the prepaid $3 / day unlimited everything plan.