One of the bolt receivers (I'm not sure what the right name is) pulled out of the seat-frame and I just got the replacement. So I liked it for three weeks and then was annoyed. If it keeps being shoddy, I'll have wasted a bunch of money.
However, I like having it when it's not broken. My shins get sore if I stay in the prototypical position too long, but there are three main ways that I use it -- 1) ass on the seat, shins on the bottom cushion, 2) ass on the seat, feet on the bottom cushion, rocking, 3) ass on the seat, feet on the rocker rails. I also swap out for any of: standing, stooling, and sitting on a yoga ball.