I have read that T-Mobile USA will not let the 7.8 update on the Nokia Lumia 710 mobile phones. If this is the case I guess other T-Mobile stores all over the world will also prohibit the update. Since I am developing an VoIP app (like this one: http://www.voip-sip-sdk.com/p_511-windows-phone-platform-voip.html) it would be great to have it on the 7.8 update but unfortunately I am at T-Mobile. I do not want to change my Lumia 710 for another WP7 OS mobile because my next phone will be a WP8 OS based one but still have 6 months from my 2 year contract.