Tired of the Google Talk rumors? Read this:

Updated

It’s official: Google has launched a Google instant messenger/chat service, called Google Talk.

Yes, Google shared the news with us a couple of days ago. Alas, they required us to hold to an embargo of this evening, 9pm, as a condition of being included. So we’ve faithfully sat on this all day, even as many other folks have reported on elements of it.

So here’s the fully story, to run in the Mercury News tomorrow….

Google already offers everything from e-mail to social networking. Now the popular Mountain View search engine company is jumping in with another popular form of communication: Google Talk, where you can instant message and chat with your friends directly from your computer to theirs.

Google also may unleash a voice service that lets you call fixed-line phones too, the company said. It’s Google’s latest effort to expand beyond simple search into a wide array of communication services. It is also taking on competitors Yahoo, AOL and Microsoft’s MSN, which already offer instant messaging and chat and are also trying to upgrade their voice communications — though it has been slow-going.

“We always thought of communications as an important part of managing information,” said Georges Harik, director of product management at Google. “”If you’re using email, sometimes you want to get a hold of someone immediately.”

You can only use Google Talk through Google’s e-mail service, called Gmail. But here’s the good news: You no longer need to be hip to get Gmail, which used to be invitation-only. In fact, analysts said, Google’s plan is to drive more widespread Gmail adoption. Beginning today, you can sign up via a text message to www.gmail.com from a mobile phone, give your phone number and get a code that allows you to create an account. Google makes money from advertising that runs inside Gmail accounts.

Google Talk’s “”messaging” allows you to write in a box that pops up from Gmail. It will rely partly on an open protocol called XMPP, which allows people to connect even from other services such as iChat, Gaim and Cerulean Studios’ Trillian, according to Harik. Still, people using those services will have to sign-on to Google’s Gmail to communicate within the system.

Also today, Google will announce that customers of service provider Earthlink will become part of the network that is compatible with Google Talk.

As for the “”chatting” part of the service, Google is using a proprietary protocol. But it plans shortly to change to an open platform, called SIP, so outside developers can contribute applications.

“They’ve put together the pieces to be a very powerful portal player,” said analyst Allen Weiner, of Gartner. The open platform distinguishes Google’s services from those offered by AOL, MSN and Yahoo, which can’t talk with each other, except for when they are used by theirr corporate clients. Google also claims that it offers superior voice quality, ease of connection and seamless integration with email.

However, it is the newcomer in a full field. An AOL spokesman said chat and messaging services are best when other people use them, and that AOL has a strong lead. AOL’s messaging program has about 41.6 million U.S. users, followed by Yahoo Messenger with 19.1 million and MSN Messenger with 14.1 million, according to ComScore Media Metrix’s July report.

The reviews are mixed. Some, including analyst Greg Sterling of the Kelsey Group, said they liked Google Talk. “It’s significant for Google because it’s been a gap in their offering,” he said. “As they increasingly take on the mantle of a portal, it’s a natural for them.”

However, some analysts said that usual “wow” factor built into most of Google’s new offerings is absent from Google Talk at least — so far. Danny Sullivan, editor of Search Engine Watch, said the services offered by competitors are already very good. “They say voice quality is really good,” he said. “But Yahoo messenger seemed to work as well for me.”

He and others said the real significance for Google is getting its feet deep in the water in an area it has been relatively absent. The launch comes two days after Google unveiled another free program that aggregates information on a computer desktop, the Google sidebar. It also comes less than a week after the company announced plans to raise $4 billion in a secondary stock offering.

Google’s Harik said the company hopes to launch a voice service that will allow people to call others at their regular phones, but that engineers haven’t figured out how to merge it with Google’s current project. Yahoo has bought a company called Dialpad which has such a voice service, but it hasn’t been integrated yet within Yahoo’s messenger service.

Update: Search Engine Watch’s Danny Sullivan has a good review, including a box showing the various messaging and voice features now offered Google, MSN, Yahoo and AOL. Minor quibble: It says AOL and Yahoo have a VoIP capability to call regular phones (not just other PCs). Our understanding, from chatting with AOL and others, is that this feature aren’t yet integrated yet into their instant messaging platforms.

Update II: Check out this more considered review (free subscription) of Google Talk by our colleague Mike Langberg. Unlike us, he is not crazed by just getting the news out, and takes his time and describes how it actually works.