I never had an iOS device previously so I cannot tell my opinion about it. I have a Nokia Lumia 710 that runs Windows Phone 7 OS. In my point of view this OS is really good, I found it to be really easy-to-use. I am also developing an onw VoIP app for it. I just found a guide that provided useful code snippets (if you are interested: http://www.voip-sip-sdk.com/p_511-windo ... -voip.html). This is only a suggestion, sorry in case if I violated the forum rules. Windows Phone 7 has also really good apps and I am looking forward to buy a Lumia 920 with Windows 8 app. I do not want to convince you to have a Windows Phone OS based mobile, just shared my opinion. By the way I do not have any problem with Android and iOS, each OS has its own pros and cons.