In 2013, the sticky feature is certainly on by default. I learned a number of Alt+ shortcuts in 2003 and have had to readjust in 2010 and '13. As I recall, this was not the case in 2007 but my memory is not always-- what were we talking about?

Pressing Alt alone in the later versions displays the tab shortcut keys in the Ribbon (whether or not it is displayed) and the numbers for the Quick Access Toolbar items. Pressing key for one of these then opens the next level, or, in the QAT, activates the item.

I still have to remind myself to release Alt before pressing the next key, such as in ALT,L,U for the template and add-ins dialogue; Alt+L does nothing.

Best,
Ulodesk