The outgoing call functionality was probably the most missed. To change from Google Talk to Hangouts, a user needs to selected the "Try the new Hangouts" option in Google Talk's menu. Fortunately, users can revert to Talk if they wish.
We have confirmed that once you have upgraded Talk to Hangouts it is impossible to place -- or receive calls -- through Gmail. The only option for Hangouts users is to make a call from the Google Voice web app, which will then ring one of their connected phones before routing the call to the receiving party.
The outgoing call feature was added to Gmail back in 2010. It's a popular -- and, for phone numbers in the U.S., free -- way for users to place outgoing calls from their computer. Of course, while Google has offered these free calls since that functionality launched, it could always change that stance.
On Monday, Nikhyl Singhal, product manager for Google's real time communication products (including Hangouts) said users need not be concerned: Changes, including the addition of the missing functionality, are coming.
Thanks for all of your feedback on last week's Hangouts launch. I wanted to quickly talk about 1) making/receiving phone calls in Gmail, and 2) Google Voice support more generally.Naturally, there wasn't a date listed.
1) Today's version of Hangouts doesn't yet support outbound calls on the web and in the Chrome extension, but we do support inbound calls to your Google Voice number. We're working hard on supporting both, and outbound/inbound calls will soon be available. In the meantime, you can continue using Google Talk in Gmail.
2) Hangouts is designed to be the future of Google Voice, and making/receiving phone calls is just the beginning. Future versions of Hangouts will integrate Google Voice more seamlessly.
On another subject that might concern some, it's worth noting that although advanced Hangouts features obviously don't work, users who upgrade to Hangouts are still able to to use other traditional Google Talk chat apps like Trillian, at least with limited support. That being said, suggestions for these clients to add better Hangouts support are definitely hitting emails and forums.