I think it would be fun to learn what becomes of O'brien. Will she die of malaria, fall in love, get her cumuppence, have a life changing experience? She's so good at being bad.
I haven't read the spoilers.
(edited by Anonymous 4576737456)
We don't find out what happens after she leaves in Season 4, but who knows, maybe in season 5 we'll hear something. For a while there was talk on whether or not the Crawleys would find out O'Brien was responsible for the death of Cora's unborn son in the first season.