We dropped npm in favour of yarn a while back, but I imagine we'll switch back once the stable release is out. Our needs are perhaps simpler than most, but the key issues we were having with npm at the time were directly solved by yarn:

  1. Dependency install was taking too long.
  2. Inconsistent builds between devs because of no lock file.
  3. Could not search the registry from the command line in a timely manner.

Having just done a quick test on a random project, I'm pleased to see that all of those concerns are now taken care of, plus the install (for this project at least) is ~30% faster than it is with yarn.