Google Voice
Log in to GrandCentral and check in your inbox. You might have a message at the top saying one of two things:
Your account is not yet ready to be upgraded. Please check back shortly.
or
[blahblahblah]
Yes, Upgrade me
When you get a chance, be sure to check out the Google Voice Suggestions and be sure to vote for the iPhone app. I also recommend suggesting the Play and sort voicemails directly in Gmail as well as the Receive calls on Google Talk option.
Also, at the bottom of that page, suggest that they bring back outbound call recording. I was a bit upset when they changed that.
Naturally, I've upgraded. I don't know if they imported my GrandCentral address book or not, but that was basically just a copy of my OS X Address Book which is now currently synced with my contact list on Google and my iPhone.