The Queen's visit to the Republic of Ireland is about time. Yes, Ireland's history is peppered by bloody events instigated by British governments of the day, but much has moved on and it is appropriate to grow up and welcome the head of state of the UK - notwithstanding the silliness of having a hereditary monarch in that role. The potato famine, instigated by Catholic-phobes from the UK, was a gross atrocity. Certainly the state sanctioned religious discrimination against Catholics in Ireland was a disgrace (and in Northern Ireland state sanctioned discrimination didn't start to be addressed properly unti the 1960s).
However, independent Ireland's history is not without disgrace. It disgustingly decided on neutrality in World War 2, whilst the UK fought Nazism. Ireland was saved from fascism by Allied men and women who fought it, many of whom died. Whilst it provided unofficial help to the Allies (and to be fair was hardly economically or technically capable of fighting a war), it was a "free-rider". For decades it funded and armed the IRA in its insurgency in Ulster and ably helped fight the British military presence in Ulster. That's without noting its repulsive complicity with covering up the rape and brutal treatment of children under the care of Catholic sadists and pederasts.
Of course much has changed in recent years. "Peace" in Northern Ireland at least has acknowledged an end to the formal claim from Dublin of sovereignty over Ulster, and it remains true that the majority of residents of Northern Ireland are unlikely to want to be part of the virtually bankrupt Irish Republic.
With membership of the European Union, and end of the Troubles, the openness of the close relationship between people in both countries is palpable. British citizens do not even need a passport to enter the Irish Republic and vice versa. There is no border control between the Irish Republic and Northern Ireland. Dublin by far the most popular air route from London's Stansted airport, second most popular from Gatwick and third from Heathrow. The largest foreign born resident community in the UK are those born in Ireland. The UK is Ireland's biggest trading partner. The economies are closely intertwined.
Given that it only took the UK and (West) Germany a matter of less than a decade to advance relations from arch enemies to being Allies, especially given the level of destruction and death each had inflicted on the other (because of Germany), it is about time Ireland grew up. Most people in Ireland have, as they have family, friends and business ties across the Irish Sea and across the nearly invisible border in the north of Ireland.