I like that the Forgotten Realms has taught me to be a better Dungeon Master.
Years of gaming in the Realms has taught me that knowing the essentials about the Realms is all you really need to take a part of the setting and make it your own for your D&D campaign. Thatís the essence of being a Dungeon Master and thatís what the Realms is best for.
Every DM wants to wow his or her players with their world building, whether itís through the Realms or via some homebrew game world theyíve created.
Learning how to manage that desire without letting a setting and its NPCs overshadow the player characters is a skill all DMs can use. Iím glad I learned it by playing in the Realms, where omnipresent/powerful NPCs and the sheer grandeur of the setting can overwhelm DMs.
I like that I know the setting. I like that itís deep enough to let me choose my level of involvement; it gives me the freedom to dive in as deeply as I want without feeling overwhelmed by it all.
Most of all, I like that the Forgotten Realms has helped me to get over the feeling that I need to know everything there is to know about it.
Remaining ignorant about large swaths of Realmslore is a good thing. Without mystery, uncertainty and contradictory details (in sourcebooks, novels, etcÖ) you lose your sense of wonder and curiosity about the setting.
Without those, you canít create, fill in the gaps and be a good DM.
Without all of these, you donít have the living, breathing world that is the Forgotten Realms.