The Martelli round about (and their other mats) are pricey - but they are fantastic. I LOVE all of my mats. Each has been purchased during their sales. Their sale format has changed, but I think they still have a sale each month for some product. Worth getting onto their email list, or following them on FB, if you think you might want something from them.
As for the RoundAbout specifically, it turns so smoothly that nothing on the surface moves. I had the green square one that was supposed to rotate, but it was so hard to turn that nothing I had on it was still lined up after I got it turned around. The RoundAbout is more like the Brooklyn Revolver as far as ease of turning, but it also has an ironing surface on the flip side.