Here's a really nice hotel, very decently priced and clean:
Jury's Inn - Christchurch (that's the name of this hotel location, because it's across the road from an old cathedral named "Christchurch".)
the website is here: http://dublinhotels.jurysinns.com/jurysinn_christchurch
My roommate's family came to visit for Christmas and stayed there, and they loved it. I visited them there, and it was nice. It's also pretty central, so you can get out and walk to many of the city's sights, shopping, and the Temple Bar district where many of the pubs and entertainment are to be found.
I went to Google street view and got some screen shots to show you...
Here's the hotel (red brick building on the right):
Here's the old Christchurch across the road:
and here's a map to show you where in Dublin the hotel is (I put a red STAR right at the intersection where the hotel is):
One of the "rules of thumb" when staying in Ireland - SOUTH of the river is considered to be more upscale than north of the river. Doesn't matter which Irish city you're in either, it seems to be that the southern 1/2 of the city has people of middle and higher class, and therefore less crime for locals and tourists alike.
So, venture north of the river for daytime activities, but whatever hotel you go for, staying south of the river may be your better bet.