Flex in the case is a good thing, provided (of course) that it does not affect the screen. I've seen more then enough shattered Macs and iPhones to realize that these rigid devices have very little ability to absorb impact.

Also, please understand that one person using one product does not reflect the quality of an entire brand. I could easily gripe about how terrible Amazon's quality is based upon two cracked screens (one of which was under mysterious circumstances) and how great Kobo quality is in comparison. But that would be complete nonsense since the sample size is too small.