To "drink the koolaid" is to blindly place trust in or unquestioningly accept something (that could in all reality by a solo cup full of poison).
So it's not so much that they're praising highly in and of itself as that they're (implicitly) praising highly because they're buying the hype without questioning it, because it's not like they've used it in anger yet or heard 3rd party testimonials.
I mean, this isn't like a kickstarter project where you have a nice video from some random person and nothing but blind optimism it can actually deliver. This is Facebook open-sourcing a library that has been in their production codebase for multiple years. It solves a specific problem that most developers are intimately familiar with, and has already been praised by people in the tech community who aren't officially associated with Facebook. It's ok to get excited about this :)
Yeah, I mean that's what I was saying I thought the definition was in my original comment. But taken the way the OP apparently meant it, it does mean something similar to "praise highly" or "very excited about." The meaning's evolved.
So it's not so much that they're praising highly in and of itself as that they're (implicitly) praising highly because they're buying the hype without questioning it, because it's not like they've used it in anger yet or heard 3rd party testimonials.