i suspect lost in this big shouting match is how misguided the question is.

its not a binary matter of "is (bb) stiffness good". it should be "HOW stiff is a good bb". (which some rightly pointed to, is a personal issue).

like everything else - and in one example, cars - there are diminishing returns. too stiff of a suspension, too low profile of tire, too flat in cornering attitude, too responsive in throttle or brake, and you harm control, feel, driveability, adjustability, grip...which sums to slower lap times.

the most germane question then is "are the current bikes on the market or in your garage stiff enough". in other words, should you ignore the pitch that next year's frame gains 7% in overall stiffness compared to this years model.......................

.....i wager that for 49 of the 50 or so unique posters in this thread... the answer is a clear YES