Leo is an IDE, outliner and PIM, as described here.
Simulating Leo's features in Vim, Emacs or Eclipse is possible, just as it is possible to simulate Python in assembly language...
The highlights of Leo 5.5
- Syntax coloring is 20x faster than before.
The "big-text" hack is no longer needed.
- Leo's importers are now line/token oriented, allowing them
- Pylint now runs in the background.
- Pyflakes can optionally check each file as it is written.
- Greatly simplified argument-handling for interactive commands.
- Documented how to do Test-Driven Development in Leo.