I really like (and find endlessly useful) Liz Keogh's scale for estimating complexity of work.

  1. Just about everyone in the world has done this - a JFDI* task
  2. Lots of people have done this, including someone on our team.
  3. Someone in our company has done this, or we have access to expertise.
  4. Someone in the world did this, but not in our organization - and we don't know how
  5. Nobody in the world has ever done this before. - Spike or experimentation needed

*JFDI - Just Flipping Do It. Something well understood that has no complexity or dependency on externality, just needs the time to physically do it.