The Forma is probably the most mainstream thing that'd survive a drop, because the TFT backplane is flexible (I can vouch for that: dropped mine
).
(Most) every other eInk screen out there uses an *extremely* thin slice of glass as the TFT backplane. A drop (among other many, many things) will pretty much kill every eReader out there.
If anything, I'd wager that a *hard* case makes it worse (I'm terrible at physics, but I'd bet it won't do anything useful to the kinetic force of a drop and how that transfers to the screen).
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Back to your Glo HD: people have been known to replace screens. There should be a few teardowns about it around the web. Again, fragile, so, have to be careful (and it has to survive the shipping in the first place ;p).
Whether that's worth the hassle is up to you.