Not sure how much you travel outside of SFO, or other major cities, but I have a few friends there with Tmoible who are very happy with the service and it provides free data & text in various places.

I think also right now they will pay your termination fees for you. Just an option. You can also just buy an iPhone outright from Apple that is unlocked. A 3rd option is to buy another cheaper phone. I did that with a "Blu" phone for a 29 day trip to Europe. Phone cost me ~120$ on Amazon (was smart with Android) and when I returned I sold it for 90$.