Aaaah, from the lighting to the shading to the shadows to the subtle reflection on the surface, that looks very good indeed Patrick. You've really progressed well in this arena. :}
The main ball reflection looks ok too. You obviously took its shape from something specific, no? Something you noticed while studying the marble outside?
I'll give you another good tip for reflections applied to non mirror-like surfaces such as this... use sillouettes. Because that's usually what the reflections end up looking like. And it's not quite enough just to greyscale a photo and use a specific blend mode to bring out either light or dark area of the photo. You need to actually manually paint over certain parts of the photo to make the a sillouette.
The main characteristic of these sillouette reflections is that, you're seeing a reflection of an environment "from the dark side" of the reflection; i.e. the light source in the reflection is behind (backlighting) the scene/objects in the reflection. Which is why you see a sillouette.
Anywho... i think that about covers it from this type of effect. The cool thing now is... you can take all of this info/technique and apply it to just about any other type of 'object' you create in PS; when/if you're after a realistic looking effect.
Well done Patrick, A+ i'd say.
PS: that link doesn't work Patrick, could you repost it please? I'd like to browse through your layers.