These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Broken Base: There are fans who love this episode for containing some serious, heartwarming and funny moments while adding some depth to Brian and Stewie's friendship. Those who hated the episode hated it because they couldn't get past the part with Brian eating Stewie's shit. Seth MacFarlane himself stated this on the 200th episode retrospective.
Crowning Moment of Heartwarming: Stewie telling Brian that he doesn't want Brian to kill himself because he's the only person in the world who understands him.
Nausea Fuel: Stewie asking (and finally convincing) Brian to clean out Stewie's diaper when they are trapped together in the bank vault...by eating Stewie's shit. Which causes Stewie to puke, and then he asks and convinces Brian to eat that, too.
Tear Jerker: Brian admitting that he keeps a gun and a Scotch in a bank vault to prepare for the day when Brian is so sick of life that he can have one last drink before his blows his brains out alone. Keep that scene in mind next time you watch any episode where Brian dying is Played for Laughs or the infamous episode where Brian gets run over by a car and Stewie can't use time travel to get him back (at least until the Christmas episode).