The Littermaid tent definitely has it uses. From providing privacy to cats to sparing the owners of seeing their pets do their thing, the advantage can very well be mutual. As in all good things, there are always downsides to consider.
Durability is in question especially if your cat decides to enter the box from the top. The plastic rods on the may not be able to hold up even to an average-sized cat. Access may prove a bit difficult when you are trying to add litter. The cost of replacing broken parts might come out more expensive than buying a new Littermaid tent.
There is one thing which the Littermaid tent has proven useful. It may not even be included in the original purposes which the manufacturer had in mind. With the presence of the Littermaid tent, the cat is forced to use the ramp instead of jumping out of the box directly. This prevents having to contend with litter all over the vicinity while the ramp keeps the litter stuck on the paws of the cat from going everywhere.