I am a strong supporter and developer in OpenBSD, as it is by far the most exciting Operating System I've ever used. However, the code should compile on ANY UNIX that libnet can be compiled and installed on. Aside from the tool, how much time do you devote to studying networking protocols such as BGP, TCP, etc. I read the theory like everyone else, but I spend more time in front of the computer than with my nose buried in text books. I'm a very demanding person in not believing theory until I've witnessed it in software.
Most people can talk about wild attack scenarios till the end of time, but can they actually do it.
Not even I can project all the uses for such a tool suite. If you can break down network theory to packet level, Nemesis has infinite possibilities and makes a fine addition to anyones' toolkit. The media is by far the biggest problem. Contrary to US Government beliefs, throwing all the web defacers, virii authors and DDoS kids in jail is not the answer. It's very similar to the drug war.