It's hard to say any one place is the "best" during a holiday to Ireland, but the stay at Abbeyglen would definitely deserve that title if it was being given out.
The entire visit was perfect. To start, we were upgraded at no extra charge to a bit larger room. This was followed by a great first & second night - it was a delight to learn a bit more about the local history, meet other guests (& bond over a few drinks and songs!), and of course, the dinner served at the castle was delicious. The town of Clifden itself was great to explore, and very close to the castle itself -- lots of good food and drink!
Everyone was superbly kind (from Brian who helped us in to Freda who gave us some advice on researching our surname), and we'd highly recommend Abbeyglen to any traveler in the area. We'll certainly be coming back!