I've been seeing more and more authors lately dismissing partial rendering (a.k.a. UpdatePanel) as a poor man's version of Ajax, something you should only choose if you're too lazy to implement "true" Ajax.
I think that view not only has a slightly pedantic ring (isn't laziness one of the most powerful driving forces in computer science? isn't it perfectly ok to choose the most productive approach in some contexts?) but also misses the point that there are cases where server-side rendering absolutely makes sense.