Think about what you’re trying to accomplish, and look at the specifications. If the goal is to produce slices with perfect uniformity, a mandoline makes good sense. This uniformity conveys a sense of quality to restaurant food, which is one source of the mandoline’s popularity.
Many mandolines I found in the stores and on line were only good down to 1/8 inch, just under 3mm. Look at a ruler and decide what kind of potato chips that would make: very thick “hand cut” chips. Some mandolines claim to do 0.5mm, which would produce standard American potato chips.
Most mandolines make very nice 3/8 inch slices, so they can make great french fries and carrot sticks. Cucumbers, peppers, small onions, summer squash and zucchini are easy to work with. Large onions, eggplants, turnips, beets and potatoes don’t fit unless you cut them to a starting shape, but that’s doable enough. You can even slice herbs and greens if you bundle them together tightly, say with a rubber band. If you want to slice tomatoes, consider that tomatoes are messy if pushed, and a rotating circular blade might be a better choice. You could freeze the tomato, but I’d be reluctant to bet my hands against a mandoline fighting anything hard-frozen.
Look for interesting results when slicing most fruits. But ordinarily you wouldn’t use one to slice citrus, except it’s a great tool for making candied orange peel. I’d stick with a knife for pineapple.
If you want to slice a roast, the mandoline isn’t wide enough. If you want to slice bacon you can’t really push correctly to get that long cut. For meats, a circular slicer looks like the best way to go, though a mandoline could slice pepperoni nicely.
A mandoline would do a great job with Swiss cheese or cheddar, but think about what would happen to a sticky brie.