Atlas CTP to RTM $() change
Microsoft made a great change with their framework. There was naming collision using the prototype javascript framework and atlas. The $() method was defined in both libraries. I wanted to point this out because I've mentioned it in the past and I'm happy they "gave in" for compatibility.
$ and $get
The CTP release defined a global alias named $( ) that mapped to the document.getElementById() function. The $( ) alias is not supported in the RTM or Value-add releases. Because we have a goal to not conflict with other AJAX frameworks, $() cannot be used; other frameworks are defining it also. In its place, the RTM release defines a $get( ) function, which performs the same task.
Read about all the changes here.