Honesty time: I loved my time at Oxford, but that doesn’t necessarily mean you will.
A semester (or, term, as they would say it in the UK) at Oxford is amazing, but it’s fast-paced and rigorous. If you are studying any humanities subject, you can most likely bet on writing an average of 3,000 words per week, on top of the various readings your tutors will assign.
If your aim in study abroad is to learn, then this might be the right place. However, a lot of people study abroad to travel and explore, and if that’s what you want, this program might not be right for you. I was lucky enough to travel through Italy with a friend directly before the semester began, and I went to Edinburgh and Paris after it ended, but your travel time might be more limited in comparison to, say, a program in London. Oxford is only a 90-minute bus ride from London, but it can be kind of a pain to get to one of the airports (Heathrow is closest to Oxford, but the bus ride is expensive, so I would recommend trying to get a flight out of City Airport). More importantly, there’s always a lot going at Oxford—in addition to all the work you undoubtedly will have—so don’t expect to be travelling every weekend.
Most importantly, while Oxford is a huge “college town” with thousands and thousands of students, it can be a bit difficult socially. Unlike a lot of universities, you typically take your classes by yourself, so there’s less of a collaborative learning environment. And while St. Catherine’s has clubs and societies, it might be more difficult to participate in activities at the University level, especially if you’re only here for a semester (rather than the entire year).
I’m not saying that you won’t make any friends. There are around 50 other visiting students who will be facing very similar circumstances as you. And Catz does a great job—much better than the other colleges I’ve heard—at integrating you into the community.
But you’re still in a really odd situation. Most likely you will be attending in your junior year. However, if you go for the fall term, you will have orientation with the “freshers,” who will likely be years younger than you and experiencing collegiate life for the first time. You will be the same age as the third years, but by now they’ve likely made their own groups of friends. Not that they won’t be friendly to you, they will! (I was lucky enough to infiltrate into the friend group of some third-year guys on the floor.) But a lot of them won’t seek you out the way in the way you made a lot of friends when you first when to college.
Basically, you need to be proactive in your social life. Make plans to get a drink at the JCR, interact with people throughout the college, etc.
If you’re the kind of person who loves meeting new people, you’ll do fine. If not, you will still most likely be fine. But you might not find it as easy to make friends, which might be a deal breaker for some of you.
If any of this makes you uncomfortable, you might want to look elswhere. And that's okay. There are so many other places to go and people to meet. It might seem cool to put Oxford on your resume (literally updating mine right now...), but ultimately, you should pick the best program for you.