Debian has a system called popularity-contest, which is an opt-in
survey of package use. I was curious to see the ranking of darcs
among Haskell implementations themselves. The results: Darcs ranks
higher than ghc and hugs.
# is the package name;
# is the number of people who installed this package;
# is the number of people who use this package regularly;
# is the number of people who installed, but don't use this package
# is the number of people who upgraded this package recently;
# is the number of people whose entry didn't contain enough
# information (atime and ctime were 0).
#rank name inst vote old recent no-files
138 darcs 563 159 280 124 0
(51) hugs 304 119 157 28 0
321 ghc6 194 81 80 33 0 (Ian
Hugs is listed in a different category, so the ranking is off.
Ian Lynagh pointed me at this nice graph showing the historical
installation of the three packages: