Google Voice offers much promise. It's just not quite ready for prime time.

You’ve probably already heard of Google Voice, but you might not be aware of what it is.

First, don’t confuse it with Google Talk. They’re both services of the ubiquitous Google. They serve different needs, though. Google Talk is an instant messenger–like product that allows you to communicate using your computer. Google Voice is, at its purest, a personal permanent phone number that you can take anywhere — from cell phone provider to cell phone provider to Internet phone service to landline. Or, at least it holds that promise for the future.

For now, Google Voice, a relaunch of GrandCentral, which Google bought in 2007, is a feature-rich telephone service based on Internet technology that you can link to your current phone service.

To start, it’s a phone number that you can give out that forwards your calls to some other number, allowing you to pick it up wherever you want. That makes it an excellent way for you to have a continuing phone number without staying with the same phone service provider. Yet, with phone number portability now mandated by the Federal Communications Commission, that part of the product is useful only in certain circumstances. It’s really the “extra” features that make Google Voice so enticing.

If working properly, Google Voice lets you prescreen your voice-mail messages in a way that most voice mails don’t allow. So you can have your Google Voicemail automatically pick up your calls, hear what the caller is saying and then interrupt the outgoing message to talk with the caller, just as your now-obsolete answering machine used to allow. You can go even further by requiring callers to announce themselves and decide from there whether to pick up or send to voice mail. And you can decide whether to do this for all callers or just for those who have blocked their caller IDs. Google Voice is smart enough, too, to remember who they are the next time they call, so they don’t have to keep announcing themselves. You can set Google Voice to do it for them. Unfortunately, however, I haven’t been able to figure out how to remove the system’s memory of who is calling, in case the first recognition is a mistake.

Also, you can record the calls that reach you through Google Voice, and Google Voice can transcribe (albeit poorly) the voice messages that you receive, making it possible to forward them to you via e-mail or SMS text message.

In short, with these and other features, Google Voice changes the way you can use your telephone.

I only wish it worked most of the time. Officially, Google Voice is still available by invitation only. And I can tell why: It doesn’t work consistently.

I managed to get five invitations — one for each member of my family. Yet, all complain consistently about various problems they have encountered with Google Voice and have begged to stop using it. The last time I looked, there were 1.5 million registered Google Voice accounts, but only 580,000 active users. The majority of registered users aren’t using it.

I suppose it’s easy to be attracted by the promise of tomorrow but doing so means dealing with the problems of today. Most people should stay away until it becomes more stable. To me, that means at least connecting a higher percentage of calls, reliably sending the e-mail or SMS alerts about voice messages, and allowing more flexibility when setting it up.

Google Voice isn’t horrible; it’s just not ready for prime time. So for a while, it’s mostly a product for tech enthusiasts or those who absolutely need one of its unique capabilities.

Still, keep your eyes peeled because some day it just might help change the world.

Editor’s note: David Radin is a national radio show host and business consultant. You can reach him at www.megabyteminute.com.