[mercurial]

It looks nice, and I assume the underlying code is less gnarly than vim's, but I don't see the radical improvement over vim which would make me switch (also, obviously, it's not going to benefit from the huge ecosystem of vim plugins).

What I think would be a killer for a vim successor would be to keep the best-in-class editor functionality, add decent extensibility (not vimscript) in the core product. Then add support for stuff commonly found in IDEs: notion of projects/subprojects, API to support plugging syntax parsers easily, source control integration, etc., and offer core plugins for a few popular languages.