All Blender's animation editors have had redevelopment for the new animation system, not only to bring it up to date with the new internals, but to add features and improve consistency.
The animation editors (and their various sub-modes) now all share more internal functionality (filtering, channels region, etc) so that their capabilities and their methods of interaction are more similar across the board. The graph editor and dopesheet can now display multiple curves and actions from multiple objects in the scene, and all editors have the ability to filter based on data block types, or selections.
The Graph Editor has seen many new additions in Blender 2.5. Apart from the ability to view and edit all animation channels for any animated properties in the scene at the same time, the channels themselves have extra functionality such as locking, hiding, and ghosting.
The workflow has also been greatly improved, with the removal of the necessity to enter 'curve edit mode' before editing keyframes, since all curves are now directly editable. A number of annoying quirks have also been removed for a smoother animating experience.
A 2D cursor has been added to better facilitate a number of transforms. It consists of the current frame indicator (vertical bar) and a value line, and can be used as the pivot point for rotation and scaling, as well as aiding in lining up and plateauing keys.
Also new are value sliders per channel (enabled with View → Show Sliders), which show the current value of each curve, and auto-key it upon editing.
Replacing the old floating panel is a new 'curve properties' region (View → Properties), for editing specific properties of the active f-curve.
The new graph editor cursor can be enabled and disabled here, which provides a pivot point for rotating, scaling and mirroring keyframes.
Also available are f-curve modifiers, which can procedurally modify animation curves with extrapolation, noise, or even generating curves from audio, without disturbing the keyframes underneath.
The Dopesheet replaces the old Action Editor and like the Graph Editor is now capable of viewing and editing multiple actions and keyframes simultaneously. Newly added is a 'Summary View' which provides an overview channel of all keyframes on the timeline, allowing you to easily view, select and manipulate all keyframes on the timeline at once.
Keyframe drawing has also been greatly optimized, with large numbers of keyframes now able to be viewed and edited 7000% faster (figure obtained for a previously unusable file imported from BVH data) than in 2.49b. Additionally, keyframes are now completely drawn using OpenGL, and can be tag certain keyframes as being 'breakdowns' or 'extremes' to understand your keyframe poses faster at a glance.
The new Non-Linear Animation (NLA) system was designed and implemented as part of the 2009 Google Summer of Code by Joshua Leung, who is also responsible for much of the rest of the animation system re-development.
Unlike Blender's previous NLA system, which was restricted to objects only, now any data block that supports animation data can also be used for NLA.