I had a Grand Central account for a while before it became Google Voice. I have no major complaints it has worked well as a number I can give out to various contacts so they can more readily contact me. This has been and continues to be an issue for me since I have Federal government clients. There are lots of rules about where I can and can't take my cellphone (especially since it has a camera).
I'm attempting to use it for all my business contacts so I can control more readily who has access to me. And one enhancement to the service I'd like to see is the ability to control the number of rings a call goes through at my various numbers. During business hours I may only want my cell phone to ring 3 times, as the odds are I don't have access to it (for a variety of reasons, such is my life). Instead of their standard number of rings, I KNOW I need a faster ring rule at that time of day. So why not let me control that?