The Allo apk hit the scene late last night and some of us have already started using it. Google should be announcing Allo at any point now.
For anyone interested, you can point yourself to APKMIRROR for the current release of Allo and join the many that are already using it.
- You can't really SMS at the moment
- You can reach people, not on Allo, seems to be done via the Play service and people can reply to you
- Offers a lot of options similar to Telegram / WhatsAPP
- Google's Assistant is live and useful when looking for information
This is just the tip, I'm sure will see more over time. I'm going to give is a good 4 months (Quarter) to see where this goes.