If the source of the filter has more than 25 entries - we will automatically render the filter control as a "Type ahead" control. This will help users narrow in on the specific value they want to select.
The control that we have that allows more free form criteria entry is the search box. If it is enabled on the table you can get partial matches, "like" statements etc. Unfortunately - the search box does not operate on a single selected column of your data - so you will probably get unrelated matches.