My only concern is that there are lots of services that do something similar to Nexus that are community made right now and exist due to the community use agreement or a special agreement made with Paizo, like AoN or Pathbuilder. As long as Paizo isn't planning on changing its community use policies then I'm fine with something like Nexus, but I can't deny I feel a little anxious being a big user of these community services that appear to be a competitor to this new official partnership.
