The side squeeze buttons need some time to get used to. Mine were stiff but now they're fine. I really had a huge problem with the MX Revolution. My hand was getting sore after trying it at the store for about 5 minutes. IMHO, the Mighty Mouse has a better shape. It's like a bar of soap. And I don't know about you, but I use soap bars every day when I shower so the shape is natural to me.