But my point is that when roaming, an agreement only exists with the 2G networks for T-Mobile and Orange, so you can't roam on the 3G version - and so a manual registration will force you to drop down to 2G.
It's fine for voice, but until the network properly becomes one around next March, you'll be restricting data for better voice/text coverage.
And, once you do roam, it won't generally search for your home network until such time that it loses the signal.