This is a subject close to my heart Ghengis.
I'm from Dublin and my dh from Kildare, we return at least 4-5 times yearly and often think will we go back.
The obvious advantage is as you say support from family and friends, but somehow that has never been enough of a good reason to make us move back.
It is expensive, and the amenities and quality of services are not as good as the UK.
That said they are a people we understand and every time me and dh return and find ourselves on one of those nights out where two drinks turns into ten and you run into lots of people you'd nearly forgotten about.........and you don't panic about the kids because your Mum has them........
In short it does always feel like "Coming home".
I think it's different for everyone, but what your line of work is and where you intend to live will play a large factor.
So far this year I've spent no less than 7wks there between Dublin and Kildare and a wedding in Clonmel. The climate isn't good and the "Celtic Tiger" is but a distant memory.
I don't want to get all negative or hijack your thread, but I do wish you the best of luck and look forward to hearing how you get on with your decision.
It is ideal to have the support of family and friends wherever possible but you have to be able to live there contentedly too.