> From an implementation POV, it's also generally easier to rewrite core parts in a lower-level language, than it is to redesign a (scriptable, deployed) UI.
But only if the data structure is simple and works well for the problem domain. Bazaar (a DVCS from Ubuntu; I mean bzr, not baz) had a much simpler and consistent UI, but it had several revisions to the data structures, each one quite painful, and it was slow; they were planning the rewrite to a faster language but never got to it. (Mercurial also used Python and wasn't remotely as slow as bzr - the data structures matter more than the language).
But only if the data structure is simple and works well for the problem domain. Bazaar (a DVCS from Ubuntu; I mean bzr, not baz) had a much simpler and consistent UI, but it had several revisions to the data structures, each one quite painful, and it was slow; they were planning the rewrite to a faster language but never got to it. (Mercurial also used Python and wasn't remotely as slow as bzr - the data structures matter more than the language).