I haven't done pre-clearance in Dublin -- but I have done it in Toronto. It seemed to go faster than immigration in New York or Atlanta, based on my (limited) experience.
But I'd still caution against it: If you hit a delay at a transfer point, causing you to miss a flight, it can be frustrating and/or expensive. And adding an unknown such as 2 immigration checks (Ireland from the Czech Republic, and then USA from Ireland) will have the potential to mess up your trip -- unless you budget so much time for it that you really won't save any time at all: You'll just end up spending that time for certain in the Dublin Airport, rather than potentially in line at JFK.