In my opinion, a potato ricer has to be one of the least essential tools one needs in a kitchen, especially if storage space is a concern. Having said that, they are sort of fun to use. For those who don’t know, a potato ricer is similar to a garlic press (another pointless tool, as far as I’m concerned), but bigger. The idea is you place boiled potatoes into the ricer and give it a squeeze, forcing the potato through the many tiny holes and into a bowl. You then add warm milk, buttermilk, cream, melted butter, what-have-you and give the riced potato a stir and what you are left with are incredibly smooth, velvety mashed potatoes, without even the suggestion of a lump.
Of course it’s a matter of taste, but I feel that lump free mash is appropriate primarily in certain circumstances, most of which I would say are formal. In fact lumpy potatoes have a rustic appeal that I think most people rather like. Unless smooth mashed potatoes are very important to you, I wouldn’t recommend getting a ricer. A good old-fashioned masher is fine.