Sony already had a great app for Android which let you chat with people, connect to your PS4, browse the PlayStation Store, etc. But I admit, when I used the app, it was to chat with other PSN people 99% of the time.
This new Messages app is great to have. I've already downloaded it and it is very nice and clean on Android. I signed in and all my messages and groups were there. The design is even material!
I also noted the speed of Messages is far quicker now than the other PlayStation app, which is great when you want to respond quickly to your PSN friends to get in on that game.