Here’s just a sample of changes since 2.8.0…
# Dashboard memory usage is reduced. Some people were running out of memory when loading the dashboard, resulting in an incomplete page.
# The automatic upgrade no longer accidentally deletes files when cleaning up from a failed upgrade.
# A problem where the rich text editor wasn’t being loaded due to compression issues has been worked around.
# Upload error messages are now correctly reported.
# Autosave error experienced by some IE users is fixed.
# Styling glitch in the plugin editor fixed.
You can also view ALL of the changes here on their trac system, and it’s a pretty long list.