Is an exercise ball really a good office chair replacement?

Reviewer opinion is genuinely split. Mainstream press and some Reddit threads on r/backpain and r/Posture report short-term posture and core-engagement benefits, while specialist subreddits including r/bodyweightfitness note that sitting on a ball is still sitting and that all-day use can cause its own fatigue. Most regular users seem to alternate the ball with a traditional chair rather than going all-in.