One of my senior class projects was a Benzoin condensation in a Room Temperature Ionic Liquid, and we got pretty decent yields.
Ionic liquids are used because they have a few properties that appeal to chemists;
they are stable at room temperature (non-volatile) whereas most organic solvents evaporate at room temperature
they can solvate (dissolve) both organic (and to some extent inorganic) molecules and compounds depending on the type of ionic liquid.
They are re-usable solvents, as you simply wash the reaction mixture with an organic solvent to "pull out" your molecule of interest, the layers separate and you are left with "washed" ionic liquid ready to go again.
They've also been shown to increase reaction rates in some cases.
Google Room Temperature Ionic Liquids and I'm sure you'll find some more of their attributes and perhaps some specific cases