The social proof didn't happen. The program was just too new and employers hadn't even heard of it yet. Fortunately, the hard skills I gained from the course were substantial enough that it didn't matter. I actually leap-frogged past where many of my acquaintances with CS or engineering degrees were. From what I understand, the current Hack Reactor classes actually are getting some significant name recognition along with the skills.
By the end of my course, I had serious interest from Google, Groupon, a Japanese game company, a cool consultancy doing cutting edge stuff with Ember and a couple of start-ups, one of which is building on Meteor. I went with Groupon, mostly because of the team and the tech stack. Another factor was that it's well enough known of a company that working there will pretty much ensure my liberal arts degree won't be held against me in the future by any but the most credential-obsessed companies. Only Google offered more in that regard, but I didn't get the impression that people there were too into JavaScript, or any dynamically typed languages, for that matter. It's possible I just caught the wrong interviewer, though.
Hack Reactor did well for me in several areas. Coming into the job at Groupon, I was being able to contribute right away and I was already familiar with the technologies in our office (Rails, Node, Backbone, CoffeeScript, CSS preprocessors, git, etc). Another great thing has been the network. I know tons of motivated smart people who are now working all over the bay area. When I set out to do a start-up, I'll very likely be teaming up with a fellow HackR Alumni. The final big help has been just a general solid CS grounding. Having already implemented hashes, trees, prefix trees, map, reduce, once, memoize, etc. has definitely been helpful. We certainly didn't learn everything, but we learned enough to have some idea what we don't know and where to go to learn more.
As for difficulties, I'd say the biggest was not being fully prepared for large codebases. It definitely took more time to get oriented and figure out where various data was coming from at work than it did on the projects I was working on at Hack Reactor. It was also a little jarring to see how OO-focused the programming world at large is, since I had been working more with functional maker patterns than pseudo classical patterns. Writing a scheme interpreter in JavaScript was one of the things I worked on as a personal project.
I don't know Java yet. That definitely causes a bit of friction when looking at general CS resources online. I'm not terribly concerned though. I'm pushing onwards, taking coursera classes and doing my best to maintain some of the momentum I've carried over from my 80 hour weeks at Hack Reactor, within the framework of a more balanced life.
tldr; The program was fantastic. It's already paid for itself and the network is amazing.