The goal of Facebook Pages Manager, from Facebook's perspective, is to separate the business and personal tools often utilized by Facebook users, streamline the interface of the core app, and make Page updates easier. But the resulting app has many crossover features, and the fact that you have no choice but to switch between apps can be frustrating at times.
If you have a Facebook Page and try to check your notifications, respond to a message, or make an update in the standard Facebook App, you'll be told to download Facebook Pages Manager. Once you do, those notifications will open in the new app. This is a frustrating feature and it slows down quick checks of your contents. The app, itself, is laid out almost identically to the core Facebook app with a list of your pages, and basic menus at the top of the screen, this time with additions like "Insights" and "Admins." The ability to access all of these menus from the home page is nice, and for those that prefer to separate home and business, the separation not only makes sense but works.
Ultimately, whether you like the Facebook Pages Manager or not doesn't matter. Its use is mandatory, and while there are some overlaps and needless restrictions, the core app is well constructed, responsive, and makes checking and updating your Pages faster and easier.