I just submitted a patch to fix an issue where using change_column with :null => true on a formerly :null => false column does not work:
http://dev.rubyonrails.org/ticket/11561
I'd like to get this into 2.1 and could use some +1 love.
I've used this in production extensively with no issues, but couldn't get tests integrated into AR's tree properly. I could use some simple tips with this part (the mock DB's confused me).
Thanks, Nate