Some feedback:
Turning this on automatically in the recent update broke some things, because the heart button on my site is “thumbs up” icon (using this official theme component). Suddenly, when people clicked the thumbs up, a heart started appearing on the left site of the post footers.
I was confused because I didn’t know that Discourse Reactions had been installed and automatically enabled, so I went into the settings to try to figure it out what was going on, and I saw a setting for default that said “heart”. I flipped it to “+1”, but just as I hit the save button, I saw a note underneath that strongly recommend that people don’t change that setting:
I tried to change it back and it wouldn’t let me. The red error message said something like “heart” not found. Not knowing how bad the damage was, I restored from a backup that I had made right before updating, which turned it all into a 40 minute ordeal.
I don’t want a heart icon to be the default icon on my site, so I hope there aren’t plans to force that change. That’s the main thing preventing me from trying it.
Side note: there is a bug here when used with the like icon theme component:

