Any tools for profiling shaders?

Hi All

I am planning to do some optimisations on the shaders we're using for our game, principally because we appear to be fill-limited on some devices. Is there an easy way to determine whether the 'cost' of shader is going up or down? I guess what I am saying is that I want to make changes to out existing shaders or write new ones - how can I tell if in principal the shader would be cheaper than it was before, or is it a case of just applying a change and observing results, perhaps in a controlled environment - i.e. spinning cubes that apply the shader?

Thanks Ian H