ANOTHER UPDATE: I took a conference call on MO+ on a cell network and had very little trouble with the call. Awesome! And! The app allows you to listen to voicemails directly in the app. Also awesome! The most needed improvements -- probably difficult to make -- would be better ability to answer incoming calls. Many calls never trigger ringing, and those that do are difficult to answer because this is an app and you have to navigate to the app first to get the call. But still this is a great app! UPDATE: I love being able to send pictures with the app now. Yea! This is a good app. Between improvements to the app and improvements to the iPhone, the sound quality and connection for outbound calls has really improved. It does present challenges for incoming calls. Very often I miss calls. And if I can tell that a phone call is coming in, because this is an application and not part of the phone itself, I have to enter my password on my iPhone, navigate to the application, wait for the application to load and allow me to answer the call. So even when I know that a call is coming in, it's likely that I will still miss the call. This still beats having another line, but anyone who is wanting to use this to know that these are the challenges that they will face. And of course if I take security off the phone, that would improve my chances of receiving phone calls, but I want the security on my phone. All in all, it's great to have the ability to make outbound calls through this app. I also do use it for texting. As others have noted, receiving text messages can be delayed with this app. But I find texting all in all to work reliably well. The other challenge I have is that I have this app on more than one device, and I don't know how routing works for incoming calls, but I never know exactly where an incoming call my come in. I would delete the apps elsewhere, but I want the ability to make outbound calls and texts, so incoming calls remain a challenge for me.