Robert Shearman wrote:

Having the index exposed for even simple operations means that the user 
has to initially learn three states instead of two. The worst thing 
about the index is that it is a limbo state. The committed content is in 
the history and can be viewed by gitk (and other tools that the user 
will be introduced to later) and the working tree is exactly what the 
user sees in their editor. Having a hidden state isn't very good from an 
HCI point of view.

Index is accessible, just like committed contents. The fact that gitk, qgit,
git-gui doesn't display state of index is their limitation.
-- 
Jakub Narebski
Warsaw, Poland
ShadeHawk on #git