I like that the aliens have senses of humor, and agendas, and do not regard humans as either yokels or incomprehensible marvels. (In the last book, the Dhryn were worrisomely ignorant of biology and how to deal with other species. As expected, this turns out to be a relevant peculiarity of their culture. Everyone else has good interspecies manners. When we see another alien get all offended about some Earth thing and run off, we're supposed to read it as strange -- and, indeed, it is.)