In Thursday's New York Times, you can read my experience with HotSpot@Home: T-Mobile's converged (unlicensed mobile access or UMA) cellular and Wi-Fi calling plan and hardware is available in only Washington state at this point. I tested the service for two weeks, and was quite impressed with overall quality, but handoffs between cell and Wi-Fi networks needs work. T-Mobile won't be rolling this service out more broadly until the hiccups have been scared out of it. But for someone who needs mobility, the fixed cost of Wi-Fi calling, and who likes one of the two available phones, it's a solid offering.
At $20 per month for unlimited calls within the US, T-Mobile can compete with Vonage on pure cost, as Vonage is $25 per month. Skype's decision today to launch $30 per year unlimited calls within the US (and Canada), or less than $3 per month, puts another spanner in comparing plans.
But let's be frank. T-Mobile is a phone company, and they know how to run a network. The intent with HotSpot@Home isn't to make a super-generic Wi-Fi offering. Rather, it's a way to lower customer costs at the same time as they increase loyalty. Their UMA offering is an integrated, single-bill package that's a double-play (fixed location, as in the home, and mobile).
Vonage still has a lot of stutters--in their business and in their service--and the lack of a mobile component means you're managing multiple phone numbers and devices. Would I drop a landline for Vonage? Hardly. And I can't drop a mobile line, so it doesn't buy me anything there.
Skype can't provide reliable service yet--it's not anywhere near telecom quality on average, although individual calls can be fantastic. I've made hundreds of hours of calls on Skype's network this year, and despite having a 3 Mbps/768 Kbps connection at my office, the call quality and other parameters for Skype-to-Skype and SkypeIn/Out calling is all over the fence. It's unacceptable to rely on for business calling without accepting that fact. I love, for instance, when calls go out of sync so there's a several-second offset between myself and the other party.
Now Skype is starting to move into the double play by pushing Wi-Fi only phones, such as those from major Wi-Fi equipment makers. Belkin's introduction of a Skype phone that can place calls using Boingo Wireless's puts them closer to challenging cellular operators. And as Wi-Fi expands to broader coverage areas, perhaps Wi-Fi will be an alternative to mobile calling for some users. But I don't buy it. Voice is very challenging, and Skype is starting already with an uneven service.
I'm watching T-Mobile HotSpot@Home very carefully, because they are the largest carrier in the world to push this as a service that they apparently plan to extend to their entire market. Their decisions in response to real-world performance will affect cellular customers and carriers in the US and internationally, and will also affect how VoIP develops in metro-scale Wi-Fi networks.
Update: British Telecom (BT) just launched their UMA service for SMBs (small-to-medium-sized businesses) in the UK. They're offering the Nokia 6136 and the Motorola A910 handsets; the Samsung P200 will be added next month. They're not offering unlimited calling for a flat rate, but the tariffs for Wi-Fi home/office/OpenZone calls are quite low: 5 pence (p) or less than US$.10 for up to 60 minutes to a UK landline; 15p to BT mobiles; 25p to other UK mobiles. Cellular rates are 25p maximum to all numbers for calls up to 60 minutes.