Version:            (using KDE KDE 3.5.2)
Installed from:    SuSE RPMs

For me it is really hard to navigate through all those groups.

I would opt for such options:
[ ] keep leaves together
  o below all other nodes (in current branch of course)
  o at the top
  [ ] group them in special tree node (for example "Final groups / leaves")

[ ] show full name for every internal node
[x] show full name for every leaf 

This way the tree could get more organized -- not it is quite common that there are a lot of leaves in a group, keeping them "unfolded" takes too much space --> thus above wish.