We stayed at the Bewley's in Ballsbridge for two nights, back in June of 2000 and it was pleasant, economical and comfortable, but I found it a bit too far out from city center for MY taste. If economics are an issue, consider the Jurys Inn Christchurch or Customs House, which are RIGHT IN the Center.
With your limited time you are probably better off to pay a bit more and stay right smack in downtown Dublin. Look for hotels in the Dublin 2 area. As Bob suggested, take a look at my Lodgings page. If you still need other recommendations let us know.
Some years ago we stayed at the Jury's Custom House. A couple of blocks from O'connor st. bridge. The hotel is clean, $ for breakfast. Has some traffic noise during the day but gets quiet at night. I think we had the 4th floor facing south. The neat thing was that we could see Sugarloaf Mt. way down in Wicklow. Plus the hotel is along the River Liffy and is just past the Business district which has a cute man made pond or what ever with benches around it for some solitude. Finally, as you walk along the Liffy toward O'Connor bridge is a Potato Famine memorial displaying a group of Irish people (caricature style). -gary
I can also recommend Jury's Inn Christchurch. We stayed there in October, 2004. It's occasionally criticized for being too much like an American chain hotel, but since we didn't spend much time *in* the hotel in Dublin, it suited our needs just fine. Comfortable and clean. And the location couldn't be beat. Our room was in the front, so we had a great view of Christchurch Cathedral, and the evening bells were ringing when we checked in--lovely!