The comments on the Yeti's are pretty much true, but to clarify. Yes they do need to be on a fairly stiff boot, mine are on Berghaus Kibos, which apart from being extremely comfortable are a B2 rated boot. As I said they are winter boots so the need to be able to take a crampon necessitated the B2 and hence the Yetis are fine.
As for the toe riding up, I have had this also, but a couple of spots of Superglue on the toe solves the problem. Again, no intention of taken them off whilst out.
As for someone spraining themselves trying to take them off, again as I've said, given its my winter wear, they don't come off, never found a need, I guess the question is why, unless you only have one pair of boots across all seasons. The Yetis mentioned with the corresponding lip on the Rand at the front were specific to a corresponding boot with a groove along the toe section. The lip helping to retain the toe of the gaiter on the boot which by their nature would be more flexible. These gaiters were also not made of the heavy duty rubber that the standard Yetis are made of, and this made them much easier to remove or put on as and when needed.
Lastly, the underneath of the gaiter has a piece that sits just in front of the heel and this can be susceptible to damage from rock etc. but its is pretty tough and in my case, my winter boot, majority of the walking is on snow/ice. I have had occasions where winter is not fully upon us and this can be a problem, but mine were bought in 1982 and are only on their second change of rubber rands which seems pretty good to me
To get them on (or off) will likely involve some broken nails and a few swear words. They are put on by first putting the toe of the boot through the front section of gaiter, don't fit the toe at the stage, leave the boot sticking out of the front hole in the gaiter. Then attend to the heel and fit the gaiter to the heel of the boot. The underneath strap may need easing forward so it is not on the heel. Finally the toe neds to pulled over the toe of the boot, this is the tough bit. In the past I have had mine in a vice whilst using all manner of blunt instruments to ease the toe over, but for me they are worth it. repeating myself, but once on that's it, they only came off to be sent away for new rands