On Lion I installed an extension which game me the ability to use middle click to open and close tabs, and I used Better Touch Tool (BTT) to use a 3 finger tap to act as a middle click.
Since using Mountain Lion DP4, and subsequently the final release with Safari 6, I am only able to open tabs with a middle click, and I have to use keyboard shortcuts or by clicking on the tab close X.
Is there anything which will give me middle click to close a tab which works on Safari 6 under Mountain Lion available now?