Very interesting beginning and one that does not bode well for Dexter's long-term future health.

Unless, of course, she decides to ally herself with him. Which is something that I can see Faith doing easily enough, should Dexter get the opportunity to actually explain/justify his actions.

Aside from Faith, I can see only Xander and possibly Dawn and/or Giles as being able to easily accept both Dexter's actions and his rationale for his own existence.

Buffy might be able to accept, while not condoning, his actions and behavior once she heard an explanation, while I think Willow would initially have a hard time accepting his existence, what with her having her own problems dealing with the darker aspects of her own personality.

All in all, an excellent series and one I'm eagerly following.