I checked out the cycling room at another YMCA in town and they had these

OMG I wasn't able to ride the thing! I didn't fall off but I was loopy! I kept looking for the lever to lock it in place I have only ridden true stationary bikes. What is the general consensus on these? Are they better at core strengthening? I am going to the only class they offer on Monday night to see how the instructors rides. I thought I would love it but I was so thrown off I felt like a needed some serious instruction.