Google Voice offers , including a powerful voicemail system -- complete with text transcription, intelligent call-handling, and a Gmail-like searchable archive of old messages -- as well as the ability to forward calls to multiple phones, switch phones midcall, and perform a slew of other tasks.

You can take advantage of these things with or without porting in your existing number, of course -- but if your Google Voice digits aren't the ones people actually dial to reach you, it's not going to do you much good.

I've been using Google Voice for almost two years now, and for the most part, it's quite reliable. On rare occasions, though, the service for short bursts of time. If your primary phone number is connected to Google Voice and an outage occurs, anyone trying to call you won't be able to get through.

Thus far, this hasn't happened much -- but it's always a possibility, and it's a risk you take when committing your primary number to this kind of service.