On a network where host names can be longer than 12 characters, ruptime truncates the names on output in its tabular form. Host names this long should be preserved, and allow the table formatting perfection to be sacrificed. Solaris ruptime does this (almost) correctly.
This is going to be fixed in the next version, currently pending one more bug that i want to fix first. Should appear in rawhide real soon now. Read ya, Phil