With the Vtok iPhone app you need both the Google voice app and the Vtok app. As you’d expect the two apps don’t always play nice with each other. The reasoning for needing the two apps is that you’re essentially using two services- Google voice & Google Talk. Thankfully, Talkatone integrates with both services so that you only need the one app. The result is a lot more stability & reliability from Talkatone for phone calls. Talkatone text messaging is a whole other story.
It was actually the lack of features in Vtok that caused me to find the alternative of Talkatone, not the lack of stability in Vtok. I wanted the app to integrate with a Bluetooth headset. This was something that just about every other app on my iPod was capable of doing. Talkatone definitely fits the bill as it not only allows audio to integrate with the Bluetooth headset but also passes along useful data such as the call time as if it the the headset was being used with a real iPhone.
The call quality with Talkatone is much better than Vtok, the reasoning is that Talkatone compresses the audio and processes it using their own servers rather than just taking the audio directly from Google. They even offer an option to increase the call quality even more with their $20/year premium plans.