Verizon Iphone 5 - Switch to T-Mobile MD655LL/A A1429

Our family has the Verizon Iphone 5, model MD655LL/A, which as everyone knows is the A1429 phone on the verizon network. I have seen numerous posts about this particular phone being unlocked when purchased. We are looking to move service to T-mobile as the plans are much cheaper and need to cut back on our budget due to a family member layoff.

Through research I have seen posts that the iphone 5 on verizon can be taken to t-mobile, but then again, other posts say that the phone can not be transferred. If we were to transfer the phone, what problems could we potentially have?

Posts I have seen all say that the 4g coverage via T-mobile would not work, instead we would be limited to 3G service, essentially making our iphone 5's work like a iphone 4. This is not a problem to us as we are on Wi-Fi service approx 85% of the time. The main concern with the 3G service would be worrying if the GPS is still going to work on the phone, as we use this for driving directions often.

Are there any other potential problems we could be facing with transferring the service over? We talked to t-mobile and they assured everything would be fine, but, we could ease our thoughts by going to a store and letting them try the phones. The nearest T-mobile store is a hour drive, so we decided to look for help online first.

THanks for any information as your time is greatly appreciated!