Overview of Ireland

Amazing search engine Google. http://www.ireland.com/en-us/about-ireland/discover-ireland/irelands-weather/
Best way to experience Ireland is to drive.

We looked at all options and decided to drive. That way, we can stop when we want and stay at sights as long as we want to. We just prefer the flexibility that driving affords us.

I have always driven. The worst thing to me would be going past something in a bus that I wanted to check out, but couldn't because the bus won't stop. :)

Have you considered hiring a driver, that way you would have some of the benefits of a coach tour (someone who knows the way, can tell you about what you are seeing and give you right-at-the-door service), but you would also have incredible flexibility to stop when you want and where you want, as well as starting each morning when you want (with flexibility to change those times each day) and also to end each day when you want. And by having time with the driver, it's like making a new friend in Ireland and enjoying the humor, as well as learning a bit about local life.

And, likely your cost would be much less than paying for a coach tour.

That's what we did a few years ago, and when it was all said and done, the price was about the cost of what we would have paid for just one of us to go on a coach tour, and we stayed in a combination of modest to very nice B&Bs and high-end castles (Ashford/Dromoland). And, when we did the math, the cost for the driver (he paid for his own fuel, parking, road tolls, overnights and meals), it was not much more than if we had rented a car and had the related costs/insurance, etc.

I am currently planning a return trip to Ireland myself. My wife and I were there in April 2002 and that was a nice time to visit. I always check Yahoo weather and that indicates the fall is quite a bit wetter than the spring. Seems pretty consistent in Dublin and Shannon, although the west is wetter than the east. From the perspective of temperature, I think you will be fine in October. We are driving again on this trip, as we did in 2002. It's a very expensive country to rent a car, but if you want to see Ireland it's highly advisable. For me a bus tour in Ireland would be torture—no chance to linger or as someone said, stop at the places that look enticing where the bus does not stop. It's really a matter of personal preference, for some the bus tour type of tourism works great.