Where to begin?! I was lucky enough to study abroad as a Directly Enrolled student at Trinity College Dublin through IES. I was in the amazing city of Dublin from early January until late May, and I can confidently say that it has been the greatest experience of my life thus far.
Because I was directly enrolled at Trinity College, IES was less involved in my day to day life. They organized my housing, and coordinated my enrollment with Trinity, meaning that I just had to show up! IES met me at the airport, and had an RA waiting at my apartment to meet me when I arrived. Though our housing had some hiccups (heating and plumbing issues) IES was VERY responsive in getting things sorted. These issues were beyond anyone's control, but the Director and staff were very helpful, and apologetic for any inconveniences.
In terms of academics, IES explained how we would register for classes, and offered support throughout the semester. As I said, because we were directly enrolled, IES played a smaller part here. Trinity itself was a bit tricky, and takes a bit of getting used to, but overall it was an incredible experience. You are in courses (modules) with Irish students, and you are learning from Irish professors, so the atmosphere is amazing.
Though our classes were not through IES, we were ALWAYS welcome to study in the IES Center, to print from their computers, or to just drop by for a chat. They planned trips for us, and had coffee meet ups during the semester to make sure everyone was settling in ok.
If I could go back and do it again, I would in a heartbeat. Dublin happens to be the hub for most RyanAir flights, meaning that cheap flights were super accessible (and encouraged!). I made friends that will last me a lifetime, and I strongly suggest that you spend your semester abroad in Dublin.