I have been using Google Voice for several years now. It is THE mobile number that I give out. During that time I have changed from using a personal mobile phone on Verizon to using a company issued Blackberry on AT&T, but thanks to Google Voice you could still reach me without ever knowing I changed phones and carriers. I can also set up my GV number to ring not only my mobile phone, but also my office desk phone, and / or home phone. If someone leaves me a voice mail message, I it is transcribed and sent to me as an email message. I can also block numbers and setup call screening.
The biggest downside to using Google Voice (and kept many people from using it) was that you had to pick a new number which would be your GV number. If you already had lots of people using you existing mobile number, this would mean informing everyone of your new number (pain). Now for $20, you can actually take your existing mobile number and port it over to Google Voice. This means no need to give out friends, family and business contacts a notice about a new number and you can enjoy the many features that come with Google Voice.
It also used to be that you had to have a regular google account (@gmail.com or @googlemail.com) in order to have GV. Now that Google Apps accounts have been expanded, you can actually set up GV with your Google Apps domain account!
Not sure what Google Voice is all about? Watch the short clip below.
[Email or RSS readers can watch here]