Voce is marketing itself as the first "Premium Wireless Service." For a $500 initiation fee and $200 per month you get unlimited voice services and text services across the United States. In addition, you get free 411 service, a new handset and upgrades every 12 months (yes, free), 24/7 mobile assistant, and personalized training and device set-up. I don't like that you don't get data in the all-inclusive plan (if you do, I don't see it on their site), but there are plenty of people out there that are spending $200 per month in voice and messaging without using data.
In addition to domestic services, Voce will also help you out with international roaming and international phones (free loaner phones if needed). It's not clear what technology Voce is using in the US, but from the phone offerings it appears to be GSM, so I'm not entirely clear why you would need an international handset, but it's cool that they'll give you a free loaner.
Here's what's important to understand about this service:
IT'S ALL ABOUT THE EXPERIENCE!
Voce will not get you any better coverage than any other carrier because they're buying time on someone's network (likely Cingular). Just like a Green American Express card has the same purchasing power as the Platinum card, it's about the experience of using it and to some degree the amenities that come along with it (I know a lot of people that have a Platinum Amex and have no idea that they get all kinds of cool services; even people that pay to belong to Hertz Number One Club Gold when it's included free with the Amex Platinum).
Will Voce be successful? Maybe. But they have to make the experience worth it in such a way that the fact that they are a MVNO is irrelevant.