I've been contacted by them before and declined because I don't want to be associated with their brand, and I've proofread a friend's book that was published through them because he didn't trust their actual editors. They do have a process that's more than just "submit anything and we'll print it", but they're not very good at what they do (books are submitted in MS Word format!?).

I think they're mostly just riding the monetary coattails of fad tech topics, they don't care if their publishings are worthless because they just print so much volume that no single book will ever be popular enough that a bad one will gain much notice, and their topics are generally so niche or topic-of-the-month oriented that there will never be enough readers for an individual book to throw much of a fit over quality problems.