Why not approximate a leave with several billboards, or an atlas? It looks to me like your billboard version simply needs some variation applied to the billboards being used to break up the uniform patterns. I think using a full mesh for every leaf will make the rendering a little too expensive...

[quote] I think using a full mesh for every leaf will make the rendering a little too expensive...[/quote]
Trees won't be using "one mesh per leaf". Instead, one mesh per group of leaves. The cost of rendering is actually slightly less expensive on mesh types as they do not require the billboard calculation.

The mesh type image has roughly the same number of polygons and is using the same single leaf texture. I wanted to do a one-to-one comparison of the two types of trees with the same materials.

Here is a wire-frame render of the first tree so you can see the polys.

[img]http://renderingsystems.com/gamedev/e_22c.jpg[/img]

Billboard trees are still going to be supported. It will be up to the user which type they'd like to create.

As a side note: The mesh types more accurately cast and receive shadows.

Thanks for your comment.