Actually, scanning tunneling microscopes come in quite a wide variety. It's possible to build STMs that operate at room temperature and atmospheric pressure, although only certain, unreactive surfaces can be viewed. However, if you do the work yourself, these can be built very cheaply. (Buying one could cost you a good $10,000.) To do more advanced work, though, you usually have to operate at very low temperatures -- such as that of liquid nitrogen (100 Kelvin) or liquid helium (4.3 K) -- and at ultra-high vaccuum. This is much more difficult.
Besides letting you "view" the electron surface of a material, an STM also lets you do neat things like manipulate individuals atoms or moltecules on a surface -- allowing you to create a quantum corral or the smallest IBM logo in the world.
Other than the obvious benefit of seeing the crystal structure of a material's surface, we can also study the electronic properties of individual atoms or molecules and even carry out chemical reactions one atom at a time.