I am studying Computer Science course at UCD and I can say that I am pretty happy with the environment and the atmosphere here. Good portion of our lectures were in the O’Brien Science Centre which is one of the newest and most modern buildings on campus. The course itself is quite demanding but doable, it gets harder and harder as it progresses towards the last year. Anyway, you get used to it, so the highest drop out rate was in first year and then way lower in the consecutive years. Campus is full of students and can be wonderful to stick around when its sunny and warm. Sport facilities are good as well, the swimming pool is one of the best I’ve ever used, I also used to do rowing in previous years. Generally sports clubs are very good, the only thing I’m not happy about entirely are the student societies, as although there is many of them, good number of them are not really active, so you’ll have to put some effort to find your thing aside from studies.
There are loads of international students, which is very nice to see and also to be able to meet different cultures. Accommodation on campus is quite pricey, so you may get it in first year, but then most people move away to cheaper sharing options in later years.