@SqlJason, & is the concatenation operator in DAX; + is not overloaded as in SQL.
As an additional point, depending on the measure being used to provide the numeric portion of this string, you may find a need for FORMAT(), which allows you to use a format string to alter the display of a numeric or date value.
@SqlJason how do you set a textbox to the value of a measure? I was able to create a measure that returns a dynamic title using your method but I don't know how to set a textbox a measure. I was able to do so using the "card" visualization but I don't want to use that visualization because it uses the name of the measure as a default title.
Chris Webb has blogged about a fantastic solution that listens to slicer values to dynamically create a title. Very similar solution using a card with no category that "sits on top of" of chart, but a little more robust.