I decided I wanted to use a bookmarklet to do the same thing, so I created a simple AppleScript and packaged it as an application bundle and protocol handler.
I can now just click the bookmarklet in my bookmarks toolbar in Firefox, it launches the AppleScript and passes to it both the current URL and page title. The AppleScript then activates OmniFocus and creates a new task in the Inbox, with the title of the web page as the name of the task and the URL as the note.
I explain in more detail on my blog, where you'll also find a link to download the .dmg:
Be sure to read the ReadMe that's in the disk image; it explains how to create the bookmarklet. It also explains how to modify the AppleScript. I've packaged it as both read/write, so everyone has full access to the source code.
Suggestions for improvement are welcome...