Here in the United States, David and I are what I would consider "low-end" cell phone users. We use our phones as phones . . . not web browsers or cameras . . . not datebook reminders . . . and not a GPS device.
In planning for our 15 days in Ireland, we felt we needed to have the extra security of a cell phone in case of emergencies as well as to make contact with various service providers with whom we had made advance arrangements with.
Our home cell service is with Sprint. Frankly, they don't do Milwaukee very well so I couldn't envision them being an option overseas. I did however look into a variety of options including purchasing a used phone and then buying a SIM card once we arrived in Ireland. Many who provide advice on TripAdvisor suggest buying a preloaded disposable phone that can be found in many local stores upon arrival.
After all of my research, however, I went back to a service I took advantage of back in 2006 when we went to the UK and my employer wanted to have access to me while on vacation. Mobal.com offers very inexpensive phones and a "pay as you go" fee structure. For us, we would use the phone for a minimal amount so we didn't need to prebuy a lot of minutes that would come preloaded on the phone.
We bought the "budget" phone for $39.95 (including s/h) with a call fee of $1.25 inbound or receiving. Yes $1.25 may seem like an outrageous amount, but when you consider it is zero if you have no use, it seemed to be a decent deal for our situation. Additionally, if you make a referral to a friend and they buy from Mobal.com, you receive a 10% discount on all calls. I had one such friend from my timeshare forum who bought one for her trip to Scotland next month, so I did earn a discount.
After the completion of our trip, I can report that we had 9 calls (3 incoming and 6 outbound) for a total of 13 minutes. Our total phone use bill came to $14.62. The availability of a signal and call clarity were very good; often better than what I have here in the US with Sprint.
We will keep the phone and use it for future international travel with the exception of Canada. You see, if you buy the budget phone, it cannot be used in the USA or Canada. You can make calls to those countries from abroad, you just cannot initiate a call from here.
Mobal.com does have other phone devices and plans that include making calls from the USA and Canada, they just didn't make sense for us and the way we expect to use the phone. For more information including their calling plans and rates, check them out at http://www.mobal.com/international-cell-phones/ .
One other thing that we did have for making phone calls while in Ireland, was our home Magic Jack. Here in the USA, they are often advertised on TV. We bought one last summer for $39.95 which included the phone and one year's use. Renewal will be $29.95 for one year or $99.95 for five. The great thing about the Magic Jack is that is used voice-over IP technology and can be used with any USB capable computer connected to the internet. All you need is a mic or headset with mic and you're in business.
We used the Magic Jack several times throughout our trip to call home. While the call reception was only as good as the internet connection, we had no real issues using it when we wanted to. The USB device is small, about half the size of a deck of cards, so it packs away nicely with all of the other technological devices we travel with.
Lastly, many people are on the SKYPE bandwagon. While a possible option for us as well, we did not use it on this trip. SKYPE requires using a computer with a camera and speaker (or headset) and usually a better than average internet connection.
I'm fortunate that I bought a small Acer notebook a couple of years ago for around $300 . . . the best money for a computer I've ever spent! It is very functional for email and fits inside my purse. It also has the built in camera and mic, and does a decent job with the basic computer processing I need while on vacation. I also have my photo processing software on it so that I can crop and/or resize photos to post along my journey.