Unless it is specifically needed for a certain purpose, I would not buy one. Certainly they can be good for backpacking, hiking and other outdoor activities because they wipe or wash clean, water doesn't harm them and they dry quickly. They are also very lightweight.
But for totes, computer bags or book/file bags I prefer other materials. I don't feel that nylon is the best use of my money, but for the person who loves them they are well worth it.