I enjoyed the time that I spent in Newcastle. Depends on what you're after, I suppose.
If you want the whole stags, hens, football and shopping in a foreign Penny's buzz then the places that cater for that are fairly rubbish - you could say the same about Liverpool and Manchester to an extent.
There's some savage pubs, restaurants art galleries and museums in Newcastle as well. The Baltic Contemporary Art Centre is fantastic. The Wylam Brewery is something to behold.
You can go further afield - to Durham and Chester-Le-Street - quite easily on the local bus or train.
Newcastle is handy for getting to Edinburgh too if the flights out of Cork don't line up.
Middlesbrough is a shithole though.