Github announced the facebook-a-like emojii reactions a little while ago. I watched. I've got an opinion now:
Here is my problem: when I ask for something or create a proposal, I need feedback to know if this is the right direction. I expect a github notification that tells me someone answerered me. A reaction does not trigger that notification so another task on my list is to go to that specific issue again and look if someone reacted with 👍 or not.
This could be solved by enabling notifications for meaningful reactions or by defining with your co-workers that meaningful feedback must be in form of comments.
Imo the ux of the reactions creates a unpleasant experience here