The round edges effect won't be very visible with just diffuse and a generalized light source. The Round Edges 10cm actually has the rounding set to 1cm.
If you enable reflection in the material, the effect will show up. I'd say a value of 2 or 3cm might work best at this scale. Attached is an image where I made the 10cm actually 10cm, and enabled reflections for the materials - you can see that 1cm is too weak (the middle cube), and 10cm too strong (the farthest cube).