One concern I have about using them for longer periods is that my right foot is noticeably longer than my left. My left foot matches on of the shoe sizes quite well, but my right foot is in between that size and the next larger size. It's unclear whether that will cause problems for my right foot. They have more size choices than most shoes, but size problems seem more conspicuous than with most shoes.
Note that they're not a close substitute for sandals or slippers because it takes some time to put them on (getting the toes in the right place).
I've spent too much time hiking and finding stock market opportunities over the past month and a half to write much here, but that should change next week.