As a Kohana user, I can corroborate the claim that Kohana-land is miles above the world of complete garbage PHP, but the community, the libraries, the robustness of the framework itself, and support from hosting providers, etc., is still far behind (say) Rails in every case.
Touching on community, that would probably be the biggest motivator for me to move towards rails in the future, well over anything the individual languages offer.
