There is the updating history and the list of known problems.
Works on Firefox 3 beta5.
Improved: Button to toggle text shadow is available in the status bar.
Fixed: Wrong XPath expressions from CSS selectors disappeared.
Fixed: Specificities of CSS selectors are calculated correctly.
Fixed: Multiple shadows can be shown correctly.
Modified: Shadows are disappeared from form controls except "button" elements.
Fixed: Firefox 3 doesn't freeze for shadowed texts aligned "center" or "right".
Fixed: Broken appearance of shadowed text in "button" elements disappeared from Firefox 3.
Improved: CSS selectors with namespace prefix are available.
Improved: Internal operations of rebuilding shadows are optimized.
Fixed: Style rules for phisical element created to show shadowed first-letter are inherited from :first-letter pseud element.
Fixed: Broken appearance of shadowed texts in pages which have style rules for span element disappeared.
Fixed: Shadows are disabled for editable documents completely.
Fixed: Wrong colors of shadows disappeared.
Modified: Shadows are disabled for editable documents.
Fixed: Wrongly overdrawing of shadows disappeared.
Modified: Shadows are hidden when the author stylesheet is disabled.
Improved: ":hover", ":focus", and ":active" dynamic pseud classes are supported partially.
Modified: Appearance becomes more nearly Safari.
Fixed: Works correctly in some environments.
Improved: Rules in userContent.css are available.
Improved: Colors of shadows which is declared in the user stylesheet without their color, are automatically calculated.
Fixed: Wrong line-breaks in bold and shadowed texts disappeared.
Fixed: Configuration dialog works correctly.
Fixed: Wrong alignment of shadowed texts, which include line-breaks to the last line and the text-align of the block is "center" or "right", disappeared.
Fixed: Broken apperarances by text-indent disappeared.
Fixed: Appearance of shadowed texts which include a line-break to the last line and the text-align of the block is "center" or "right", are corrected. (If the shadowed text includes multiple line-breaks, broken appearance is still there.)
Fixed: Appearance of boxes which has "text-align: center" or "text-align: right" rule is corrected. (maybe)
Fixed: Broken appearance of texts with shadow and bold disappeared.
Fixed: A mistake on specificities calculation is corrected.
Improved: Text shadows are not re-rendered for resizing of window height.
Improved: Useless strings in copied version of shadowed strings disappeared.
Improved: Specificities of CSS selectors are available. Cascading for "text-shadow" property works correctly.
Improved: Multiple pseud classes and pseud elements are available for each element.
Fixed: Useless redrawing disappeared when loading is canceled.
Fixed: Stupid positions of shadowed texts in tables are corrected.
Fixed: Freezing when many text nodes are in a element disappeared.
Improved: Internal operations are optimized.
Improved: "~" combination, CSS3 attribute selectors and :not() pseud class are available.
Improved: @import rule is available.
Improved: Absolute units of CSS length are available (as 72dpi).
Improved: Creation of dummy elements and attributes for pseud elements and classes can be prevented. (set "extensions.textshadow.silhouettePseudElementsAndClasses" to false)
Fixed: Implementations for :link and :visited pseud classes are improved.
Modified: Multiple shadows are drawed in each time.
Modified: The node is completely restored if no shadow is applied.
Fixed: Dropped implementation for @media rule backs.
Fixed: The order of redrawing becomes same to drawing.
Fixed: Wrong position of floated boxes disappeared.
Improved: Some pseud elements (:first-letter and :first-line) and some pseud classes (:first-child, :last-child, :first-of-type, :last-of-type, :only-child, only-of-type, :empty, :link, :visited, :root) are available.
Improved: Works on Firefox 3.
Improved: Rendering results becomes like Safari.
Improved: Shadows are automatically re-rendered after resizing of window.
Fixed: Broken appearance with line-breaks disappeared.
Fixed: Long inline boxes are correctly shown.
Fixed: Hacks for Safari (ex. Slashdot.jp) are ignored correctly.