Structurally, the WB Yeats is a fine ship and she sails very smoothly.
However, as you have probably read there are a lot of niggles with this ship.
1) The whole feel of the ship is open plan almost everywhere. There are no nooks and crannies just to chill out, read a book, listen to your iPod or whatever. There is a relatively quiet observation lounge on one of the upper decks, but it feels like it was put in there as an afterthought.
2) In June, July and August the ship feels like a floating creche - screaming kids everywhere. So May is a wise choice.
3) Unfortunately, the ship inside feels like a cross between a late 1990's call centre and a really cheap version of an Ikea showroom. The Oscar Wilde ship felt a lot more classy.
4) The fixtures and fittings feel very cheap. One chair in the main bar which I sat on, the back of it just sank beneath the seat. The plastic coverings used to cover screws in the bunks also just seem to fall off! The bathroom door in my cabin had already two screws missing on its hinge which meant the door was not flush with its frame.
5) The public address / speaker system is atrocious. It sounds like something out of Das Boot - producing an awful tinny static-infused sound.
6) The entertainment setup in the main bar (traditional Irish music band) felt very improvised. The band, while good, were just sitting on some chairs surrounded by a retractable belt barrier - the kind that you would find at a bank. No elevated stage - they just seemed crammed in the corner of the bar.
7) The deck layout plans posted in the public areas are a joke. Unbelievably, on first boarding the ship, I was trying to locate my cabin only to be told by a crew member to ignore the cabin map because it's wrong! He kindly gave me directions instead.
8 ) The standard cabins do feel more airy and have more comfortable beds than BF which is nice.
9) The food in the self service restaurant was fairly industrial. I opted for the chicken curry which was very average. The next morning in the same restaurant, the Irish breakfast stewing under hot lamps the next morning looked totally unappetising. I opted for a coffee instead.
10) There is a decent amount of outdoor deck space to roam around. The view of the Wicklow Mountains on your left as the ship travels up the Irish Sea is spectacular - and was one of the highlights of the trip. Arriving into Dublin Port is also very interesting, as you get a birds eye view of the now decommissioned Pigeon House Power Station.
The sailing I was on in early July was relatively busy. I think the WB Yeats might be a much more enjoyable ship in an out-of-season crossing. The online booking facility offered by Irish Ferries is highly intuitive and much quicker to use than BF. Moreover, I had to make a last minute change to my booking and the Live Chat agent - implemented it in less then 3 minutes. Highly impressive.
Overall, it was not a bad crossing but Irish Ferries really let this ship down by doing it on the cheap. It felt like the fit-out of the ship was managed by cost-cutting accountants who were trained by Ryanair. I hope BF do not make the same mistake on their new builds!
As for Dublin. Nice city, friendly locals. The city centre is around the same size as Amsterdam (centre). Currently experiencing a tourist boom, hence hotel prices can be high if booking is left late.