Older TES games didn't have these kinds of shadows. Oblivion had tree shadows and creature shadows. The creature shadows were so insignificant that they didn't have to add this kind of optimization and the tree shadows were... well they weren't really shadows as we know them. More like slightly animated decals. The shadows they cast were independent of light sources. You could even be hovering above a tree and it would somehow cast a shadow on you.
I am finally happy they added shadows , but come on, snow accumulation is one basic shader nowday as well , if I am not wrong the engine still misses ambient occlusion , a proper material offset parallax mapping working , the normal maps usually look all like having a shiny surface wich looks odd and weird , no Subsurface scattering , and a lot of other things , but the snow shader ( done in its simplier way of flat texturing involving only the z top flat surface shoduln't be a problem , now look at the shader models in openworld like red dead redemption that is even bigger , when it rains small pools of water pop out , mud comes , and dreis out , look at the snow , the footprints ... and if you want to go even higher look at uncharted 2 snow effect ... http://www.youtube.com/watch?v=tILaq47iX4s&feature=related or the sand effect in the 3rd chapter ...
for nottalking of the flat water , the water looks nice but honestly are just couple of morphed geometry with a rolling texture scrolling one over the other to give the illusion of water movement and is not really a shader...