We're going to Ireland later this summer and have Verizon service on our (US) phones. The Verizon plan has an International option for $10 a day per line which wouldn't be cheap exactly but would probably be worth it for the convenience if the service would be decent (relative to the locales we'd be in). When we traveled to Germany and Scotland a few years back we got SIM cards for a European carrier and that worked well, but we'd rather not mess with that again unless it'll give us superior service availability.
Thanks in advance for any experience you can share!