I don't like the new Google Hangout integration with my gmail web app. It's too busy, too much color, and too hard to see what status people are. In short, get off my lawn.
Can I get the old Google Chat interface back?
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As of 2017-Jun-26, the old Gchat is completely removed from Gmail. You are now forced to use Hangouts.
-- As of 6/20/2017, this answer is no longer accurate, but retained for reference. This functionality has been removed.
Yes, you can revert to the old Google Chat interface.
First, click on the down arrow next to your name/icon. It will bring up a menu of settings (like the picture below). Second, click on "Revert to old chat". It will reload the Gmail webapp, and will open a short survey where you can explain why you don't like it.
As with other Google interface changes, this may not be permanently available.
From Hangouts Help Page:
Turn off Hangouts and use Google Chat: