It really does look like a nice framework, I'm working with this too.
As you say, there does not seem to be a way to retrieve the lastname and firstname through the API, but that is a minor issue for me (I'll probably need to extend some of the objects anyway).
I've noted that the firstname and lastname attributes will only save when creating a new user, so calling userAction.save for an existing user will only save changes to the required fields, not the optional ones.
Generally you would manipulate the identity store directly, however while this is trivial with JPA it's not so straight forward with LDAP, etc. If you raise a feature request then I'll look at adding some extra support for this kind of thing.