We are excited to announce the release of Zotero 4.0. Zotero 4.0 is a major update over 3.0, offering many new features and bug fixes, including:
Tag colors
On-demand download support
Relative path support for linked files
Automatic style updating for all installed styles
Automatic journal abbreviation support
Firefox 20 compatibility (Zotero for Firefox)
…plus much more.
See the 4.0 changelog for more details and a complete list of changes.