Pros
Hack Reactor has/had (there's been a huge exodus of staff recently) some of the best people that I've ever worked with. They assembled an incredibly impressive group of people that were smart but also nice and knew how to work on a team. The students are also great. Hack Reactor does a great job of churning out software engineers that aren't douchebags.
Cons
I loved working for Hack Reactor until the founders came back and took over running the place. They had a super strong leadership team of smart, compassionate, hard-working people that they displaced due to their need to control every element what was happening in the program. They hired these people to run Hack Reactor and then micro-managed them until they all left in disgust and frustration. The biggest problem Hack Reactor is facing right now is the egos of their founders. They are simply out of their depth in terms of running a company and constantly make mistakes, but because of their egos, they won't admit their mistakes and don't get help from seasoned professionals. Over the last 3 months, almost half of the staff has left because the situation there has become unbearable. It is heart-breaking to me that a place I loved so much has demonstrated that they really don't care about the people that come through their doors. Turns out their high-minded mission statement was just talk.