The Start button was removed for R2012b.
The toolstrip - here tab apps - is supposed to address the need for the Start button better. That is for the "find something quickly" use case.
If you need something even more often, you can create a shortcut. This means both uses cases are addressed my looking at the top area of the MATLAB IDE. I personally find this preferable and not using the start button was an irritation for me 1-2 times.