Yes, a tree might be a bit much. However, something like a saguaro cactus from a photo, to get a basic 3D shape in obj form, to then detail in 3D-Coat or Zbrush -- might work pretty good. But the darn demo won't save, is limited to something like 4 minutes of work -- or session time (don't remember exactly, but it was a short time) four textures, etc.
I really don't understand why some developers cripple their demos to the point you can't really test them (especially cheap products that would sell rather easily if they "work".) I mean this isn't an application that creates an end product (or if it is, you can't tell if it is because you can't output the model to render out and see.) What it tells me is if they did let you test it properly, it wouldn't be up to par and hence the low price. So I was hoping someone had tried the full version.