as the EAGLE acronym says it's an Easily Applicable Graphical Layout Editor. It's a very lean program that offers absolutely reliable tools for PCB design. The user interface is the same in all editor windows. It does not matter if you are working in library for creating components, or in the schematilc editor or in the layout. Once learned, you will be able to master every situation.
One of the greatest benefits is our very active community. Simply take a look into our newsgroups or into the Download area of CadSoft's web server. There are lots of user-contributed library files or User Language Programs for almost every purpose. By the way: The EAGLE User Language makes EAGLE very flexible. The User Language gives you access to every object of your schematic/board /library. So, for example, complex actions can be automatized. There is certainly more to be said about EAGLE, maybe there is one or the other EAGLE user that wants to share his opinion?