Rated 4 out of 5 stars

Apparently, Firefox 4 has finally implemented this functionality so you now get 6 similar (and basically duplicate) items in your context menu: 3 from Firefox (in your browser's lang), 3 from the add-on (in English). Sadly, you can't just uninstall the extension because the built-in feature is not as powerful: it will not detect e-mail addresses and it sometimes misses some web site addresses. So text/plain is still necessary though it could benefit from some tweaking. Too bad it looks abandoned :(