what kind of business are you considering it for? why would you make a change from what you have?
I`ve been using RingCentral for approximately 3 months now - took the jump and said "good-bye" to the high charges from AT - and I`m very happy with their service.
I have a dedicated 800 number and it rings to my cell phone. And if I`m not available to take the call, I receive a VM pending notification in my email in box and can then listen to the message through my computer.
All calls that come in are documented also...
And I just noticed today that I can also get a free (always nice!) fax number with my monthly service.
In closing, I was really impressed when I first noticed the Ring Central ads as I do feel that their service is perfect for small businesses.
Hope this helps