Hangouts for Android is receiving its first Play Store update - on a staged rollout basis - today, fixing a few notable bugs, and promising enhanced performance in unspecified ways. Here's the rather short changelog:
● Fixed a problem where you could receive two notifications for a message: one from Hangouts, one from the old Talk app.
● Audio issues in video calls on some Android 2.3x (Gingerbread) devices, including the Droid Charge, should now be resolved.
● Bug fixes and better performance.
The double notification issue isn't one I'd heard of, but obviously that'd be quite annoying if you were experiencing it. The Gingerbread-specific audio fix is also probably welcome, considering the rather large number of Gingerbread handsets that are still out there.
Once again, it appears Google is rolling out the update on a staged basis, meaning it is unlikely you will see the update on your devices for another few days (or longer, if issues with the new build become apparent).