Pros
DrFirst isn't a place where you can come to your job, do the minimum work possible, and enjoy prolonged job security. So if that's what you're looking for, you'll probably agree with a lot of the negative reviews for the company. But if you're the type of person who rises to a challenge, enjoys being given responsibility and projects that impact the company's success, and wants to gain professional experience that will be applicable to any future job, you'll fit in well with the company.
Cons
In any mid-to-large-sized company (like DrFirst), there will always be some levels of frustration with the bureaucracy, "passing the buck," or differing attitudes towards work. Really, handling them just comes down to your level of professionalism and understanding that these aren't unique to any given employer.