Unity 3D 2.6.1
If you got frustrated because Unity 2.6 crashed when you tried to paint trees, a new version is out that fixes that bug among other things.
On a related note, I completed the excellent tutorials by Will Goldstone and purchased his book Unity Game Development Essentials. If you do the video tutorials, you know the basic project of the book. However, where the video shows you 1 way to do something, the book shows you 5 more detailed techniques. His video and book are the best thing I have found to learn Unity so far.