Inspired by Mihai's discussion of Google Bookmark's XML importing interface, I whipped up a quick bookmarklet for exporting one's bookmarks from del.icio.us to Google. The greatest benefit of this approach is peace of mind, as communication between del.icio.us and Google is entirely client-side. (Note that this has only been tested with Firefox.)

The steps:

• Add this bookmarklet to your browser, by bookmarking it or dragging it to your bookmarks toolbar: del.icio.us to GB.
  
• Go to del.icio.us' export page. Alternatively, you can just click on settings->export/backup once logged into del.icio.us.
• Click on "Export"
• This should present you with a download box for a file named something like "delicious-YYYYMMDD.htm". Save it somewhere on your computer.
• Be sure that you're logged into Google Bookmarks.
• Open the saved file using your browser. And give the bookmarklet a little click. it should be accessible via your browser bookmarks or from the bookmarks toolbar. This should zip you to Google Bookmarks' import page, now fully populated.