So yeah, for example: content assist, code snippets
("Templates" in JDT lingo), preference pages for all that,
outline and quick-outline (no hierarchical outline support
though).
However, no Junit view, nor package explorer support. Well not
for displaying Java-like flat packages at least, but there is
some support for other Project Explorer extensions: stuff like
project dependencies and (in an upcoming version) build
targets. I dunno how well that applies to Scala though.
No code folding support either (DDT has that functionality,
but it's crappy code copied from DLTK that hasn't yet been
cleaned-up/refactored, and put into LangEclipseIDE).
One interesting thing that LangEclipseIDE has, that doesn't
come from JDT or JDT-like IDEs, is functionality to help you
integrate external, command-line tools to provide IDE
functionality. For example in Goclipse, the outline is
provided by an external parser (updated on the fly as the user
types in the editor). Again dunno if that would apply well to
Scala.