I ordered one large Heather Grey to start with and liked it so much that I ordered five more of various colors.  They are all well made and comfortable, but there is some size variation from shirt to shirt which I notice in the fit of the collar.  At $9/each (I got mine slightly cheaper during a Father's Day promotion), though, I think that they are a great value.  They have relatively thick material, and I like how they fit.

I normally wear a size medium, but I tend to like my tees a bit larger, and one of the reviews stated that they shrink a bit.  Having been bitten in the past by shrinking shirts, I went with a size large and am happy.  I haven't noticed any shrinking, but I've only washed them all once so far.

The Khaki shirt had a large amount of staining on the inside surface (which isn't present on any of the others), but it isn't visible on the outside.  I mention it because it might be an indication of quality consistency, but I'm happy with the one that I got.

As a note on the material - I originally ordered one because they are listed as 100% cotton.  However, the Heather Grey shirts are 90% cotton, 10% polyester.  At first, I was upset when I got my first one, but it was so well made that I quickly got over it.  The Khaki and Navy shirts that I ordered are 100% cotton as described.  If you want 100% cotton, though, avoid the grey.