I have quite a few trees. Some of the 'Old Wood' ones from Traveler over at RDNA, like the Sugar maple or his Birch.  I also have Lisa's Botanicals Oak Trees and Pear Tree from when they were Plat Club items.  

The traveler ones are pretty inexpensive.  I can't find the 'Old Wood' ones at RDNA now, so strange, but here's a Real Deal Tree...

 

http://www.runtimedna.com/Traveler-s-Naturals-Real-Deal-Trees-Vol-2.html

It has some varigation done with different maps, but I thought the ability to control the colors in this shader is a real plus.

Here's a link to the documentation of the Daz shader which shows more of the functionality.

http://3dimensiondigital.com/locker/NatureShader/NS-Documentation.pdf