For my tuppence worth, I think Irelands roads are still being developed so it's too early to get the Sat Nav, maybe in a few years.
Two examples of Sat Nav getting it wrong.
1. Car coming from Cork to Bunratty, turns onto the Limerick Bypass, road not on software, the driver eventually ends up near the ferrybridge on the N69 (Coast Road) flags me down looking for directions.
2. Car travelling Limeirck to Sligo, Sat Nav guides the driver into Galway rather than turning for Tuam/Claregalway at one of the roundabouts near Oranmore.
This was some back so the software may have improved but you can't beat a good map and the excellent roadsigns on Irish roads.