It's interesting to note in studies comparing spaced repetition vs. massed learning, when students are asked afterward which method works better, they more often choose massed even though their own test results favor spaced repetition[0]. The upshot is people can use spaced repetition, it can "work" (in the sense that they remember the material better and test better) yet still drop it thinking massed practice to be superior.
This is another way of say "everyone that it works for gets good results"