If I looked at the sand in the filter, what should I see?

[waterbear]

Actually, I once again have to disagree (and I know what I am about to say is not a popular position here on the forum) When the grains get eroded they round off and lose the sharp edges that collect the dirt. There is less turbulance and breakup of the water paths between the grains and faster water flow, hence less filtering ability. I know Ben does not agree with this since he has said that some new filter sand has rounded grains.
A slighly dirty filter WILL filter better than a clean one....this is the same idea as adding DE powder. It makes the water paths between the grains smaller.
My 2 cents!