pretty much abandoned

If you enable Google Search History Google will remember all your searches and list them on a page. This is achieved by rewriting the links using a javascript.
That script a "onmousedown" event. But due to a bug in Opera, "onmousedown" isn't fired on middle clicks, so the page doesn't get rewritten.
To make it work with middle clicks you have to change "onmousedown" to "onmouseover" using a proxy server like Proxomitron or a userjs.

Proxomitron rule:

Name = "Google - search history"
Active = TRUE
URL = "www.google.com/*"
Limit = 11
Match = "onmousedown"
Replace = "onmouseover"