As a partial solution, it turns out that IE7 seems to mostly behave the old way by changing the setting in internet-options/general/tabs for "open links from other program in" to be "the current tab or window"
After making this change, $url now follows the active tab when there's 1 instance of IE7 open, and /url -an
http://www.yahoo.com now opens a 2nd browser window instead of adding a new tab into the current browser. However, $url still doesn't want to move away from the newest browser window opened.
As I said before, it would also be nice to add a switch so mIRC will open an extra tab in the existing browser window, as well as being able to open a brand new browser window or open the webpage in current tab.
