What I would like to add here is that, there has been a test conducted to analyze the normal user's approach towards the Unity interface sporting Ubuntu 11.04 Natty Narhwal. The participants of the Canonical sponsored survey were:
P1, 19, a student and Mac user,
P2, 33, an administrator and Mac user,
P3, 25, a student and Windows user,
P4, 32, a teacher and Windows user, and some others
They were given a bare metal installed with Ubuntu Natty and asked to do some basic tasks with the system. They were supposed to be new to the Unity interface and had to be from different platforms.
To know more in details visit: ubuntumanual.org/posts/288/unity-visually-appealing-and-usable-steep-learning-curve-user-survey