If you provide an error message, without providing some way of getting the actual details of the error that occurred easily, then that is almost a hanging offense.
Saying "Oops, an error occurred, try again later" is essentially useless. Especially after you've seen it more than a few times. Moreover, this kind of thing I have seen first-hand leads to some bizarre magical thinking on the part of users, on the order of "If I slaughter a rooster, and sprinkle the blood around, and a white goose flies overhead, the problem gets resolved." It's staggering seeing some of the "workarounds" that customers will invent if there isn't real error information present.
Saying "Oops, an error occurred, try again later" is essentially useless. Especially after you've seen it more than a few times. Moreover, this kind of thing I have seen first-hand leads to some bizarre magical thinking on the part of users, on the order of "If I slaughter a rooster, and sprinkle the blood around, and a white goose flies overhead, the problem gets resolved." It's staggering seeing some of the "workarounds" that customers will invent if there isn't real error information present.