Having completed Hack Reactor in December 2014 - I've decided that now is a good time as any to write a review. Initially I wanted to hold off writing a review because I was skeptical if I "really" learned that much and wanted to see if I would be well-prepared working as a software engineer in the real world. I just started a new job as a front-end software engineer at OpenTable a couple of weeks ago and I can honestly say that Hack Reactor was as good of a preparation as I could have hoped for.
One of the best parts about Hack Reactor is that it not only teaches you very practical skills (e.g. using Git, Grunt, and various other command-line tools) but it also helps you develop a working foundation on CS (e.g. data structure and algorithms). Like many others have pointed out, the curriculum is well-designed and you will be surrounded by motivated classmates (many of mine had worked as professional software engineers prior to Hack Reactor, and I ended up learning many things from these classmates among others).
I'll be honest, there were definitely a few bumps along the road: the internet connection went down and was unreliable for a while, some of the lectures were personally not very helpful for me, and in my opinion there's too much structure in some places (e.g. requiring students to be on-site at all times, strictly enforcing 9AM attendance after staying late coding the night before).
Overall though, it feels nitpicky to complain. Before I went to Hack Reactor, I was working in a totally different industry as a management consultant and had a tiny bit of programming experience. After graduating, I was able to find a job in about a month and feel confident about picking up new skills as I develop as a software engineer. I know Hack Reactor always talks about this idea of "learning how to learn" and it sounds cliche but it's so true. At the end of the day, web development is evolving so quickly, the real value of Hack Reactor is not that you learn the latest MVC frameworks such as Backbone.js and Angular.js (and they are), but it's the ability to pick up a new framework, tool, or language on your own because you've been doing that non-stop at Hack Reactor for three months.
If you enjoy programming and want to make a career out of it, I can't think of a better or faster way than Hack Reactor.