We got one when DS was around 6months old & it's been priceless for us! I guess you could wait til bubs is born & decide what works for you & then see if you want one. They have so many uses than just feeds but each bubs is an individual so you may not get as much use out of it for whateve reason.
DS was a heavy baby & would not settle well at night first up so we got it as we were sitting in his room on a kitchen chair feeding & that was not comfy at all. We got it so I could rock him in comfort etc & do night time feeds as once he got more alert it really wans't practical to go into the lounge & let him fully wake up. For us it's been great, DS didn't sleep through the night til after 2yrs of age!!!!! so we've been feeding during the night using the rocker for a long time. He also was very sick for most of last year & it was again priceless with all the wake ups & un-settled nights. When then moved it to the office & up until yesterday were using it at the office desk..very comfy.
We moved it out when he went into a bed as it took up too much room, but we still got a rocker type more funky chair from IKEA that is still in his room as he still needs cuddles & quiet time etc.