The Luas is frequent which makes up for a lot, but the schedule is given as (every X minutes) and often misses that due to sharing with road traffic for large parts of the track.

Still better than bus eireann, where if you're getting on in the last 25% of the route, the timetable is often every hour, +/- 30 minutes, which means there could be a bus at any time and it's not likely to be the scheduled time.