I've used a thudbuster on a (folding solo bike) and found it quite good as long as I concentrated on spinning; if my cadence was faster than I could manage I started to bounce - but this happens with a rigid post as well.
My (cheap, generic) suspension post on my old hybrid was also pretty good).
I've had much more problems with suspension forks with no lockout.
Although I don't have a suspension post now, my wife will definitely have one when (if!) we upgrade the tandem.