Same Question from me as well (but I did find a workaround).
The former 3 column default theme was good and I had based a child theme on it for my site, where I also used the Activity widget from 1.1.x
Once I upgraded to 1.2, no activity widget was available. Making matters worse, the Backwards Compatability Plugin seemed borked … and my child theme no longer worked … (Using the BC default theme did not work either. navigation was totally fubar)
I have since dumpped Backwards Compatability plugin and upgraded many of my own themes to work for my needs.
I’m currently using Randy Candy (unmodified) on my site and have setup a home page workaround, using Shortcode Widgets…
I have shortcoded a simple RSS widget assigned to read the Activity RSS feed, and placed it into the content of my default page. This is a temporary fix, untill a remake of the old 1.1.x Recent Activity widget can be implemented.
