I've been futzing with the new calling service that Google is offering and will report some of the things I've experienced.
On Google Voice -
1. I got a phone number for them. I searched on my area code, 217, and my zip code. Neither of those gave numbers. (Champaign-Urbana is not a big SMSA.) I eventually searched on my first name. That provided several numbers. I chose one with a 312 (Chicago) area code.
2. I have it set to ring to my cell phone. That works quite well.
3. If calling from the Google Voice application, I can have it use the cell phone and that works fine. My other alternative is to have it use Google Talk. That doesn't work. I'm not sure why.
4. I haven't tested enough on the transcription application to see how reliability it is, but the way the text and audio are displayed is very good in my view. Somebody who used this application repeatedly would become sensitized to the need to caption video for universal access.
On calling from Gmail.
1. I have many Gmail accounts and have tried this on a couple. On one without a Google Voice account, it seems to call from a phone number that exists just for that call. If from the number that was called I try to return the call, I can't. So to me, since so often you get voicemail instead of getting the person, it doesn't make a lot of sense to use the service without having a Google Voice account.
2. When you have a Google Voice account Gmail knows this and uses that number.
On them together.
The interface is a little weird at present, since it is another browser window (or tab) rather than seeing it all from a unified view (like an inbox and a sent items box in email).
At present, none of this is available on my iPad. For browsers others than Chrome one has to download an extension to enable the calling functionality. But otherwise, this is pretty interesting and I think I may use it for real in the near future.