We stayed at the Merrion in May, 2009. It is close (walking distance) to St. Stephen's Green, Trinity College, shopping and pubs. Although we intended to go out to several different pubs in the area, each evening we ended up returning to the Cellar Bar at the Merrion. They were so accommodating and friendly, and we didn't have to walk, or be driven, back to the hotel.
We were a small group (5), with 3 rooms and everything from check-in to check-out went smoothly.
On our last day, we visited Newgrange, about an hour and a half each direction from Dublin. We had a fantastic opportunity to see the "tunnel tombs" built over 5000 years ago.
I would highly recommend staying at the Merrion.