I've lived in New York, Dublin and London among other cities. Moved back to the states in 1987. Since then I haven't let more than 5 years pass without a return trip to Dublin. I admit I'm a city kid but I do like the countryside too, and that said Dublin is one of my favorite places. To properly enjoy it you need to studiously avoid the touristy places: O'Connell Street, Grafton Street and the quays and nearby environs (ie, Temple Bar). These are where the hotels and tourist traps are concentrated. Go a few blocks off Grafton Street, for example, and you'll find some decent cafes and a few good pubs. Trinity College has a nice old fashioned campus and is mostly safe from tourists--they go to queue up for the book of Kells and then leave. If you head toward Merrion Square you're in a mixed small business/residential neighborhood that's often very pleasant. Check out the Peppercanister Church. Stephen's Green is a tourist attraction but also heavily populated by Dubliners, and there's a lot to see and do nearby. I like to head west from Merrion Square on Nassau street , take a left on Dawson Street, hit Hodges Figgis bookstore and then poke around in the sidestreets between Dawson and Grafton Street--lots of small shops, cafes and a few good pubs to explore. Head across Grafton Street, maybe go up to South King Street or the Powerscourt center to the George's Street market then along Aungier Street to John Gunn's camera shop (to buy more film).
Howth is worth a trip--the DART train goes right there. It's a proper fishing village (or started out that way), and still pretty photogenic. I lived on the south side, so I favor places like Sandymount, Blackrock, Dun Laoghaire and Dalkey--all easily accessible from the DART. If you jump off at Dalkey, you can hike up Killiney Hill for one of the best views of Dublin to the north and Bray Head to the south. Go up there at sunrise or sunset. And you can ride the DART all the way south to Bray, a cool old seaside resort town.
The counties just south of Dublin are excellent for exploring. Wicklow is full of small villages and some dramatic open landscapes. Glendalough is stunning scenery and ancient stone structures, but go in the morning before the tourist buses arrive. And if you've rented a car, County Wexford is worth exploring. I'm particularly fond of the Barrow River valley down around Graiguenamanagh.
And Ireland has motorways. You can fly cross-country or up to the wee north in good time. Get off the motorway and onto the local roads and you start encountering 1 1/2 lane roads with mammoth hedgerows on either side that can slow you down. Still, I used to drive my Mini from my place in Dundrum (Dublin) to Tralee in about four hours before the motorways went up. Concepts of distance there are very different from those in North America. (When I arrived in Tralee my friends there would offer a hot shower and ask if I needed a rest.) I'm guessing from your location identifier that you might be in Canada...?
I've done a few bus tours and sworn off them. I always found myself lagging behind or straying away to shoot a photo of something interesting (like, without the heads of tourists in the frame) and being scolded by some tour guide for holding up our progress to the tacky gift shops. Never again. So my advice is to dispense with the tours and buy some reputable guide books and design your own tour, do it at your own speed and be ready to split off from it when something interesting catches your eye. Public transit is very good in the east of Ireland, less reliable as you go out into the countryside. There's good rail service to Galway and Cork and up to Belfast; less so to the more remote places. Cars are problematic for some of us because of the need to drive on the left, but the more difficult problem is that Irish drivers, as in much of Europe, are accustomed to smaller cars and have a much more acute sense of space that permits them to squeeze through tighter situations that others might think were impossible. You might well find that driving on the left is less frightening than you thought it would be. Just remember that turning right on a red light could be fatal.
Just my two eurocents' worth.