As a junior, I was limited to only four classes that I could take abroad, and UCD was the ONLY school that my home university let me transfer all four classes from. In all honesty, that was the reason I chose to study at UCD, as culturally it's not a great fit for me. I love the convenience and liveliness of a big city, and Dublin feels quite small and UCD is far from city center. Despite this, I spent most of my weekends traveling (I was able to have a 5 day weekend with my schedule), which was amazing. I think I've visited 9 different countries in the 12 weeks I've been here. The school also provides ample opportunities to travel around Ireland for free, going to Galway, Belfast, and other attractions.
In terms of academics, for such a large school, I have felt very supported by advisors and administration. It took a little while to get used to the class sizes, which can be five times bigger than classes at my home university, but they're pretty easy to adjust to. And it can be easy to skip lectures, but most of my lecturers were fairly interesting and engaging!
Finally, I think my favorite memory, and proudest accomplishment, since coming over here was driving on the left side of the road along the western coast. As an American, I was so nervous about driving, but it was pretty easy. We did see a double rainbow over the Cliffs of Moher, so maybe that gave me some luck while driving!