Coinciding with that email, Google has posted a blog about Google Voice. According to the blog, simply follow the steps provided in the email and away you go. I plan to activate my Google Voice account soon. I'll let you know how it goes.
We're emailing you today to let you know you should upgrade your account to Google Voice.
GrandCentral is now Google Voice. We also added the following features: SMS, voicemail transcripts, conference calling and low-priced international calls.
As we focus our development efforts on Google Voice, we require that you upgrade to Google Voice now in order to continue using your number. Please log on to your account at grandcentral.com and follow the instructions in your inbox.
After you upgrade, you will be able to continue accessing your old messages at www.grandcentral.com, but all your new calls and messages will be accessible at www.google.com/voice
Google is encouraging users to pick a number that means something to them. It has even created a "number picker tool" to help users match words or phrases to a particular number.
In you have a few moments, be sure to check out this video, which provides an overview of how it works: