Here's another try at physically-based wood, but this time Maple instead of Red Oak. I added a side-by-side image with the end-grain of real hard maple magnified 10x. You can see my shader is close but the scaling is a bit off. I felt like my result was pretty good even with a slight departure from the reference. It's pretty interesting that the spotty part evens out to a nice wood color when you zoom out to normal size. I hope you enjoy it.
As always, the material ball is from JC Levet (although I modified the scene to remove stuff that is out of camera): http://www.blendswap.com/blends/materials/galvanized-steel-shader/