Im giving it two stars since its free, but a lot of us travel both north and south, and there appears to be no way for search for places or postal codes (even the second largest city in Ireland, Belfast!) in Northern Ireland. And yes, Ive tried both the UK and Republic of Ireland search.
From the Navfree support forums, this seems to be an ongoing problem, with questions about it from over a year ago.
Also, the search server for Ireland seems to be down a lot (has it ever actually worked?) - you cant search for a particular address when its down. You can still view towns, but try planning a route between two houses in Dublin without address search.
It looks like Ill have just to pay $85-$90 for the Navigon or TomTom app.
plinden about Navmii Offline GPS