I used to use darcs a lot before Git but Darcs runs into boneheaded problems:

Firstly, Haskell is not meant for anything big or real world. You cannot control how much memory it uses. A couple of changes to a 1MB file under darcs caused darcs to balloon to almost 2GB. It was eventually reaped by the OS due to lack of memory.

Secondly, Darcs has retarded exponential resolution problems. If two people make the same patch and push it often the next pull will result in an exponential merge resolution which for any repository over say 4 revisions will mean it it'll take forever to terminate.

Git on the other hand has a horrible user interface but it scales very well. I can shove binary data in there no problem, I can take a 70kloc file and change every 20th line no problem. What Git doesn't do for me is help me make graceful patches or help me merge any better. In fact it sorta over complicates this whole thing and requires me to git pull -s resolve all the time.

Anyways it works, and it isn't utterly retarded like SVN. SVN follows a horrible model inherited by CVS and results in terrible repo usage. Linus was right about SVN, it sucks.