I find that closing a question as a duplicate is very cumbersome.
For instance, if I already found a duplicate, I have the URL. I don't have the question ID or title directly. So instead of doing what would be easy, I must paste in the url to the edit box, and remove
http://stackoverflow.com/questions/ from the url, then go after the number and remove
Also, see this slightly related post Greasemonkey: Easier vote-to-close for duplicates (editor's note: 10k-only); I ask why is this not actually implemented in the site?