I have been using this plugin since about 2010. So, I've had quite a bit of experience with it. And since I'm a developer building sites for clients, I needed something I could count on and use where I could restrict access to many various areas of the site (to insure that plugins don't accidentally get deleted or updated unknowingly, same for themes, block access to areas that could allow someone to do something they shouldn't, etc.).
I literally don't know where I would be or what I would do without this plugin. It's a lifeline plugin for me. It allows me to know that what I build for a client won't become destroyed or blow up due to a client's accidental visit and tampering into an area of the website that could be dangerous. Of course, some clients are provided full access, but having the ability to discuss this with a client and provide only the level of access that is needed is absolutely wonderful.
It's also great to be able to create many various custom roles and apply specific permissions to each one, exactly as I need.
I'm sure you'll love this plugin as much as I do.
"Just remember to tip the developer." If you find, love and use any of the free plugins, just remember to share the love. (There's nothing worse than finding a plugin you love, and then because of a lack of love shown .. the developer abandons ship. So, .. if you find, love and use any free plugins, remember .. the more love the developer feels, the more likely they will be to stay around, which benefits everyone who uses their plugins.) You can also consider purchasing add-ons if they're available which is another great way to show your appreciation and support the developers. Sorry for this extra comment .. but I just wanted to share my thoughts.