Leaves look much better indeed. Steve was right, it's the roughness that's on 0.8 by default, but for leaves I always set that to 0.2 or so, and reflectivity to around 0.4. You can also add another variable for reflection and translucency values (as to color input) to get some natural differences in shine and translucency. A power fractal with sizes like 0.1/10/0.005, with noise like mix 1 or perlin, and colors like 1 and 0.5 or so, taken through a transform shader set to world, and plugged into the needed inputs in the default shader, will do just that.