A few days ago a buddy asked me why Google Voice. This was my response:
There's no hugely obvious reason to switch to google voice, but by switching there are some really nice features that you don't get with a regular cellphone number. The biggest reasons for me are:
1) I hate voice mail, and google voice allows me to view my voice mail visually by signing into Google Voice online, and managing it there. Google also transcribes your voice mail into text. Same with text messages. If you lose your phone, you can sign into google voice, text all your buddies, and let them know what's up.
2) Google voice allows you to manage different contacts in groups. Basically that some people (friends) receive different treatment by the system than others (your boss, future employers, etc.). You can record different greetings, set up different privacy schemes, etc. using groups of contacts. Of course the contacts are identical to the contacts you have in Gmail.
3) Call forwarding. You can forward your google voice calls to whatever number(s) you want. If I go home for the weekend, and I decide I don't want to take my cell with me or if I don't get service, I forward the calls to my parent's phone. If I'm at work, I can have all my calls ringed to my work phone AND my cell phone - and then answer whichever one is more convenient at the time. If I'm in Puerto Rico for a week - I can send all my calls to the place in PR - people call my usual number, but the phone in PR is what rings. Call forwarding is nothing new, but google voice allows it to multiple phones, and it's a lot easier to manage with the online interface.
4) I chose a number local to my parents. Now they can reach me on my cell phone by dialing a local number from their landline.
*UPDATED 8/18/2010*
5) Total integration with the Android Mobile OS. Basically, you don't need to buy a text messaging plan anymore. The only downside is that your friends and contacts who don't have Google Voice won't be able to take advantage of mobile-to-mobile texting...so your texts are going to count toward their text messaging package (but not yours!). Tell them to go get a Droid and sign up for Google Voice!
Here's a good article to read that pretty much says the same thing I just said:
http://lifehacker.com/5304800/google-voice-is-cool-but-do-you-need-it
