My understanding is that after the unification of the various kwan under the Kukkiwon the basic library of techniques that each school employed became relatively uniform. I've seen firsthand, however, how much two people working with the same technique set can diverge in the details and understanding of what they are teaching and how they are teaching it.
When I talk to my instructor (who is jidokwan) about Tae Kwon Do, he talks about distinctly different flavors and philosophical differences behind the schools, how they train, what they emphasize, etc. I have heard as well different views on what exactly these differences entail and am curious: What are the modern differences between the various kwan, and how does this manifest in what/how they teach?