There are not many alternatives to Google Voice out there. If you can find one (Skype?) that works like a phone, can call any phone, and offers PBX (private branch exchange) functions that you like better, by all means use it. The power of Google Voice is too great to dismiss.
I give my Google Voice number out to businesses and vendors. I give my real number to family and friends. This way, if a business / vendor becomes obnoxious, I can mark them as spam and never ever hear from them again. It also lets you screen calls, transcribe voice mail and send it to you in email or text message or both. It can ring multiple phones when a call comes in, and many other features. Think personal customizable PBX.
I will be keeping this one.
Next up: Google Sites