Thanks for the quick response. I know about .prop() and have already updated my site to use it.
My ticket is about .attr() and the code that was added to make it backwards compatible and the comments that were made about it in the release notes for 1.6.1, specifically:
"However, once jQuery 1.6 was released... Therefore, in the interest of backwards compatibility and the usefulness of the .attr() method, we will continue to be able to get and set these boolean attributes with the .attr() method in jQuery 1.6.1."
I don't see how returning different things between the different versions maintains that compatibility.
Not a massive issue for me that my site is now fixed but I just thought it incorrect as I did have to change to prop() to get my site to work with 1.6.2.