I use Vonage and Skype in flight quite a bit (and will continue to do so as long as still possible). Communicating was a pain when I first tried to do VOIP without the proper noise-cancelling equipment communicating; however, after using better equipment the issue went away and it didn't seem to annoy anybody around me either. Then again I limited my talk time to those hours were passengers around me were awake and/or meal times.

Mobile phones, however, I can see causing more of an issue especially if the cost is on the low to reasonable side.

By the way, I love Connexion, and it will be missed by me.