Not the reactions you were anticipating perhaps - everybody loves living in Chat after all, right? You can now use emojis to react to messages. Its natural silliness is offset by good uses and reveals something about Google's view on communication.
Couldn't be simpler: Hover over any message sent by you or somebody else, and click the emoji button. Select an emoji. Done. Works on mobile too.
There doesn't seem to be a reasonable limit to how many emojis per message can be sent, you can send each emoji once though. Submitting again will remove it - you know, just in case your finger slipped.
Crucially, emojis do not count as a message, so you will not get notified.
For expressing yourself
For voting (up/down vote etc.)
For saying you read a message, when that counts
For saving everybody an additional message.
This last part is important: Chat is rapidly replacing other forms of communication, such as email, so naturally the email overload transforms into Chat overload.
Reactions do not count as messages. Since their information content is limited, that is a great idea! It saves you from having to check on your rooms and wade through the "Agree!" messages to make sure you are caught up.
Write something you would like to vote on
Include icons with an explanation
React yourself (like casting your vote for all options)
This feature is not an invitation to be unprofessional, this is a company after all. Yet even if you are not the type to replace everyday nouns with images or send cats with heart eyes, a thumbs-up may save you and others some time. Thank you for reading!