Quick edit or create excerpts for both Posts and Pages, auto-generate and append excerpts or replace the content with excerpts.
Excerpt Editor has been tested on WordPress 2.5 and 2.6
No conflicts/incompatibilities have been reported so far.
The use/display of excerpts depends on your theme - more Information. You can replace the full posts with excerpts (either real or auto-generated) by setting the "Replace Posts" options in the plugin.