Sorry for the self-reply, but instead of a shameless self-bump, I have a follow-up question.
Reading through the developer forums and the 2.6DR Javadoc, I noticed the ProfileMap and UserProfileModule-classes that would seem to indicate that the ability to create custom profile attributes is coming in 2.6. Is this assumption correct?
In 2.4 I think that you are able to store any property name you want - it's not strictly defined anywhere like "theme" prop. Just some of them are mapped to "jbp_user" columns and ProfileMap use UserImpl methods to store them in hibernate mapped pojo.
For 2.6 you will be able to define user properties available in the profile. Although it'll be defined in portal configuration so not mutable on the runtime.
but how to search frm the map collections