Creative, right-brained individuals can now easily become map makers themselves using the CS:GO authoring tools. Valve's announcement specifically notes that creators don't need to follow the standard CS formula. Gameplay-affecting changes can be baked into any map, letting players create an FPS experience more to their liking.
Quality custom maps are already bubbling up.
The new maps workshop also includes a variety of social and discovery features. Players can subscribe to a map and automatically receive any future updates or revisions. Community-made maps can be rated, commented and more. Users can discover new maps by game mode, or sort by highest rated, most recent and a variety of other criteria.
The intrepid individuals at NeoGAF have already made note of a few notable new game modes, including control point capture and sniper vs. terrorists.