If the browsers would allow the login box to be styled via CSS like the rest of the UI, I think you would see more use. We finally went to SAML for our REST service authentication and have been pretty happy with it. THe nice part about SAML is an identity server provides the auth endpoint, and your app proxies the token to the identity server for authentication and authorization, it gets your app or container out of the game of authentication and authorization. Further many app servers can plug into the identity server therefore providing container managed security gates.