I think it fits very well in the software domain. The exact numbers are not the important fact, but rather as a guiding principle of what takes more time than the other.
It is not hard to think of a few examples that could follow the principle:
- Creating demo-ware software will take 20% of the time, creating production grade software will take 80%.
- Creating 80% of a system will take 20% of the time.
- 20% of a systems functionality will be used 80% of the time.
- Resolving 80% of the defects will take 20% of the time.
- Once you have done the 80% normal cases, fitting in the last 20% exceptional cases will take 80% percent of the time.
- 20% percent of a systems developers create 80% percent of the working functionality (Hopefully not :) )
I know these are crazy numbers. And I know this is certainly not true in a lot of cases. But still, you'll benefit if you keep Pareto's principle in mind.