Review (3/5): Adheres well to file and fog is easily dealt with
It's adhered to the tiles in my shower for months, and that's exactly what I wanted. It's easy to adjust so long as you are moving it when the tiles are dry. It's obviously not a genuine mirror as a heavy glass mirror would not work. I run a hot shower and I don't see the mirror getting foggy with any consistency. When it does, I find that I can swipe it with my hand and it's fine. I use a squeegee on my shower tile when I'm done and this has a low-enough profile that I can just lightly graze it while I'm squeegeeing the tile and not have much disruption.
Update: after about a year, I couldn't clean the haze that built up on it. Because it adheres directly to the wall, you have to do some occasional cleaning to keep mold at bay. I found a superior option in the Shave Well Company Deluxe Anti-Fog Shower Mirror, which hangs on a tiny hook suction cup. Because it hangs on a hook, that mirror can be removed and run under the shower water, thereby washing away the fog and keeping the mirror clean. And, since only the single suction cup attaches to the wall rather than the entire mirror, that mirror doesn't risk getting moldy.