I currently really like it and i prob will have this take over my google messenger app. I'm just reading some articles and for some reason People don't like it and idk why. I personally like how I can text anybody now with cool stickers and voice and all that. I'm taking about people outside the country as well.
IMHO, this app shouldn't have been released in its current state. This reminds of when BlackBerry released the half baked PlayBook and Z10.
You can't save conversations in case you switch phones. Sucks if you are waiting for a Note 7 replacement or plan on upgrading soon or switching carriers.
It doesn't have true SMS backup or support which is why you can't make Allo your default messaging app. This means you have to use either Messenger/Hangouts or a third party app for true SMS conversations with iPhone users that haven't installed Allo.
You can't quick reply on the notification drop down menu or lock screen on Allo which is an Android 7.0 feature.
No desktop or web client - I am actually ok with this if they are still working on it and need another 6-12 months to get it ready.