T-Mobile's WiFi VoIP service still being tested

T-Mobile is ironing out the kinks in its HotSpot@Home service, which lets users with WiFi-enabled cellphones make calls on open WiFi networks, if available, and switches them over to the more expensive cellular network if they leave the range of the WiFi signal.

Today's New York Times continues its earlier intro to VoIP over WiFi phones with a new article that discusses reactions from early testers of the HotSpot@Home service from T-Mobile. To sum up the article, it says that it's a promising technology that isn't yet up to snuff:

Call quality was excellent on all Wi-Fi networks tested, including full-duplexing — better described as the Robert Altman effect — in which both parties are speaking at the same time but can hear each other clearly.
Roaming, however, was far from acceptable. The cellular-to-Wi-Fi handoffs worked most of the time without interruption to a call in progress. But most Wi-Fi-to-cell transitions caused a dropped call as the hot spot signal ebbed with distance.

The subjects in the article eventually canceled the service after the test period due to dropped calls, high battery usage and inconsistent WiFi connections. They haven't given up completely though, and would reconsider if the mixed cellular & VoIP service quality improves.