I am not going to lie but as a Google Voice customer for a long time, I am very disappointed with this update. It is just a design change and I hope they will roll out several new features slowly.
For example I still would like them to add a feature where I can add credit to my Google Voice account through the phone app.
Among the top three features they have listed as new in the blog post, I feel like that those functionalities already exist on the current iOs app. Lets see.
1: Easily check messages, calls and voicemail(s)
Already there. Using the same top left corner main menu.
2: Keep in touch with group messages
This already exists as well. You can start message threads with multiple people. Except the media support I guess.
3: Save time with transcribed voicemail
This feature is already available. In current version, go to Menu -> Voicemail and you will see transcribed messages in your inbox.
I am honestly very confused if this just a teaser in to what is about to become a major project within Google or just a marketing team being busy.