Hangouts 4 for Android is still not done but getting closer to an internal beta, so don't expect it quite yet.
The versions I tried in the last few weeks performed like crap too, probably even slower than v3, and if released like that, I will without hesitation slam it for that. Historically, Hangouts has been probably the slowest Google app I've used, and I just don't see it getting any better.
Some examples include:
- Sending SMS. Sometimes you press send, then 15 seconds nothing happens. Then finally it pops into the chat view saying "sending" and finally sends. What the %#$^ is taking so long for the UI to update with the message I just typed?
- Seeing a conversation getting marked read. I click into an unread conversation. Click out. It remains bold for a good 2-5 seconds sometimes.
- Loading chats in general - sometimes very slow, piece by piece. You can see like 4 different chat areas load independently from each other (avatar, conversation, bottom bar, text inside the input field).
I really hope they concentrate on performance next, but don't count on it at v4 release.