I am using it right now. I love the concept because it let's me have the people I video chat, IM, and text all in one space. It also has all those emojis.
Unfortunately it is pretty laggy on the s4 and is missing a ton of SMS features, but I am sticking with it. Hoping Google will fix the problems.
Sent from my SAMSUNG-SGH-I337 using AC Forums mobile app
I used it a few times. Seems to get laggy trying to select attachments or open links. But there doesn't seem to be support for MMS, at least I can't get it to work. Just says sending for a long time then gives me the option to resend. You can send MMS to non-cell numbers like google+ contacts via the hangouts. But in 4.4 KitKat i hear its better integrated with the messaging app, and is a good replacement.