Unfortunately, online reviews are most often where people display their stupidity in public.
Jewel cases are inherently easy to break or crack -- they can be just as fragile as the discs they hold. These style of cases store discs well, in they are not made for rough handling either. My guess is the people leaving the negative comments had unrealistic expectations.
There are definitely different quality grades to jewel cases, but they are all more or less the same. The only jewel cases I would consider "premium" are the ones used for individually cased blank DVDs, such as ones used by Verbatim, Apple or Maxell. Now those are nice!
Stores like SuperMediaStore are great, but Effectuality
is known to carry premium-graded empty cases. I've not bought jewel cases from them before, only the DVD movie cases.
Check out the TDK and Maxell cases on Amazon