When I switched to Verizon and cancelled my AT&T wireless service it was because the most important feature of the phone - actually making a phone call - was challenging at best with AT&T in the Orange County area. Calls dropped constantly. And I even lost critical minutes responding to an emergency at home because of an "out of range" issue just a few miles from my house. I never regret my decision to switch to Verizon.
One of the challenges that came with Verizon is the lack of simultaneous talk and surf capability. I can't email an attachment or something to someone I'm talking with. It reduces the phone's capabilities such that I resort to waiting to get to my computer to have certain calls I could otherwise have if talk and surf worked- which is a big marketing point AT&T has in it's favor. And this really detracts from the point of being "mobile" on a Verizon iOS device. According to Gizmodo, this is still a problem with the Verizon iPhone. I can vouch for it being an issue with Verizon and KDDI (AU) in Japan as well.
Enter Line2. I was on a call today with AppleCare in the US, sitting in a Starbucks in Kobe, Japan. During the call the AppleCare representative asked me several times to try things on my iPhone to resolve the issue- which I was able to do. At the end of the call, my iTunes Match on iCloud was working again. And I realized I was doing all of this while talking via Voice-Over-IP on a really poor 3G connection. No LTE involved. I was really happy. I used Line2 because I wanted to call an 800 number for AppleCare in the US. Because of this experiment, I'll now use my Line2 number in the USA whenever I expect I'll need to talk and surf at the same time. All of this costs me just $10 per month. Add that with Verizon customer service and reliability and I'm sold.
Isn't it great living in the future?