Be careful with old versions!
These versions are displayed for reference and testing purposes. You should always use the latest version of an add-on.
* Open With items added to the context menu of the bookmarks menu and toolbar
* Automatic browser detection for Linux
* A second widget for the new Firefox theme to restore missing functionality
* Locale file overhaul
* Options page overhaul
Full changelog: https://github.com/darktrojan/openwith/compare/VERSION_5.3.1...VERSION_5.4
There are also a number of minor bug fixes.