I love GrandCentral. It's a great service. Free call forwarding and messaging service that records your voicemails. I have a comment line for my podcast (412-567-7606) and, although no one has used it yet other than my collaborators, we're happy with the way it works.
So when I wanted to find a way to make local Pittsburgh calls to my girlfriend (who has a cell phone with a San Antonio 210 area code), we thought adding a GrandCentral 412 phone number to her myFaves (her "5") would work. Plus there are lots of blogs that swear it works.
Well, it didn't work for us. Instead, using GrandCentral just ran up her precious minutes instead of granting the "unlimited calls" we expected. Here's what her contract says:
myFaves plans require minimum one-year service agreement and are available solely with myFaves-enabled handset. myFaves plans allow unlimited nationwide calling to any five US phone numbers (excluding 411, voicemail, toll-free, 900, calling card, and customers’ own numbers; and single numbers allowing access to 500 or more persons), each of which may be changed a maximum of one time per calendar month.
I think it's that 500 or more thing that blocks GrandCentral from being allowed on the myFaves. So if it's still working for you, more power to you. It didn't work for us so I say don't believe the hype. The blogs I've read about this are wrong.