The academic part of life was good. The tutorial system is great, lectures were OK, practicals were good. The selection of courses was great. But doing CS, there were few opportunities to socialize with people in your degree - you see them in the lectures, then you go back to your college. And that isn't great - perhaps it's good for people that are doing humanities and need to 'network', but for anyone doing anything interesting, you are not going to find too much in common with an undergrad studying English literature and more interested in drinking and pointless gossip/small talk.
And even many in the CS degree did not seem to have that 'hacker' mentality - that was mostly seen in international students.
What I found shocking is that so many students were doing poorly academically. The coursework and the exams were not super challenging, especially given that you chose so many of the courses, so you were mostly studying the actual things you wanted to study. Given that Oxford was supposed to have the very best students, passionate about their subjects, it was really odd how little so many cared.
Again, very strangely, few undergrad students from England seemed to go on to do Master's or PhDs, but many international students did. The graduate-level environment seemed much better, too.