The documentation for Emacs+ states that Ctrl-X 0 will not remove an editor if it is the last instance, but I noticed for the following scenario this is not the case.
Steps to recreate:
1. Open two editors 'A' and 'B'.
2. Switch to 'B'.
3. Use Ctrl-X, 2 or Ctrl-X, 3 to split the editor. You should have A&B in the first view stack (B should be selected), and B in the second.
4. Select editor 'A' in the first view stack.
5. Use Ctrl-X, 0. Editor A should be closed even though it is the last instance.
This isn't the behavior if you were to use Ctrl-X, 0 after step 1 above, so I think this might be a bug.
Env details:
Windows XP (ughhh)
Eclipse 3.7.1
Version: 2.8.0.RELEASE
Emacs+ 3.6.2