If anything, it's even tougher to predict how ordinary users will react to Reactions as a feature, or how it will affect the way we communicate in general. Will users feel compelled to pile on the bandwagon when they see a post generating amazement or laughter or anger among their peers? 
When Facebook rolled out the news feed in 2007, its users nearly revolted; now it's the backbone of the big blue app. Of course, Facebook is much bigger now, and the change could be the equivalent of Coca-Cola messing with its secret recipe, as Bloomberg puts it.
Reactions in the countries where it's been tested seem to range from neutral to positive, at least as far as I could find. A writer for Mashable in Dublin said Reactions seemed natural and straightforward when it came to news stories and other more public content -- but "it was a bit more difficult when it came to the personal."
A friend posted that his girlfriend had left him and I spent ten minutes agonizing over whether I should add a sad emoji (too pitying?), angry emoji (that might just rile him up!) or the "wow" one (this could have the subtext: wow, you're bad at relationships). In the end, paralysed by my choice of emotional reactions, I ended up commenting ("Take it one day at a time, dude.")
We'll all find out soon. Meantime, if you live in one of the places where Facebook Reactions actually has already rolled out, I'd be interested to hear from you
Either contact me directly or let us know in the comments below what you think of the changes.