the bumbo came out after my last baby could already sit up, but man, i wish i had had one for both of my kids! they were very strong right from birth, held their heads up, and could bear weight on their feet. both my kids were major proprioception seekers from the get-go, but they also needed the vestibular stim of being in the sling quite a bit. they had to be upright. both my kids started being able to sit up around 4.5 mos, but they werent reliably steady until about 6mos. when i had to shower, i had to lay them flat or put them in a bouncer seat, both of which made them scream bloody murder. a bumbo would have given me 30 mins each day to shower and get dressed. so while i never used one, i wish i had!