Google Voice does a number of things far better than any other system that more than make up for whatever deficiencies the author believes it might have.
I will preface this by saying that I am a Sprint cellular customer, so Google Voice can be fully integrated into my telephone service.
1. My cell number is integrated in to Google Voice. This means that I can answer calls from anyplace I happen to be logged in to the desktop version of Gmail or have the Google Voice app installed. This means that I do not need to have my phone tied to my actual person 24 hours a day. I can answer a call while I'm reading on a tablet in my bathtub or while my phone is charging in another room.
2. Google Voice transcribes voicemails so that they are delivered as E-mails, so that I don't have to listen to them. This is worth actual money to me. I hate voice mail with a passion.
3. I dislike SMS messages because, again, I don't like having to have my telephone permanently anchored to my body. Google Voice allows me to filter and deliver SMS messages as if they were E-mails and to respond to them as such. SMS messages never hit my phone. I've never opened the SMS app on it. I just respond to e-mails. Again, this is a tremendously valuable service.
If I'm missing something from not having texts delivered to my phone, I don't know and I don't care what that is, because as far as I'm concerned, Google Voice is doing every single thing I want it to already.