Let's give some examples of hard problems first: designing a version control system, writing a complex revenue simulation model, designing an algebra for arbitrary data model customization, etc.
If this is true then why is a VCS written in C (git) not left in the dust by Darcs?
I'm pretty sure there are several VCSs written in C that are left in the dust by Darcs, and keep in mind that git adoption got a head start from being promoted by some guy named Linus Torvalds. (Perhaps you've heard of him?)
If this is true then why is a VCS written in C (git) not left in the dust by Darcs?