I already play D&D and run a great campaign. Why should I care about Eberron?
Nobody’s saying you have to, but it’s neat to see a setting that really encourages players and DMs to make the most of the d20 rules. From mages and orcs to psionicists and dinosaurs, Eberron takes full advantage of 3rd edition D&D. Expect more opportunities to use your skills. The “cinematic” emphasis promotes more roleplaying: characters in the middle of a major city may suddenly find that Charisma is actually a useful ability. You can include all those things in your existing game, of course, but Eberron offers a fresh start and background material to help you create exciting adventures. Finally, Eberron has been designed with accessibility in mind. If you pick up the sourcebook and start a new campaign, this would be a great time to invite a few new players to the table.