Christy O'Connor Jnr is doing a lot of work here. I think he's excellent, although his work might be a bit American for many on this board. Eskerhills is a super course set amongst the esker "dunes" of the midlands and is well worth a visit. Hard on the legs, though. Mt Wolselely, Glasson and Galway Bay are his other designs of note. He raves about Galway Bay, but I've heard it's nothing special. I like Wolselely a lot, but haven't played the others.
Mike
I think the next nine holes in Carne are to be by the sea. I think this would be a great addition as the dunes are more subtile here and would give up a different style of hole, maybe appealing to those who aren't enamoured with the high-rolling holes of the first 18. Ruddy is the obvious choice, as he was involved in designing a sister course in Rossapenna. Jim Engh is also a member of Carne, so maybe... This is wild speculation, though. I don't think they would have the budget for a major designer, unless they were willing to work for challenge.
Hackett didn't always go out to build a masterpiece, as sometimes he had no budget, but he produced enough superb courses on no budget to suggest he was pretty special.
Then, as mentioned, there's Merrigan and Craddock. After that, I don't really know. Merrigan did Tulfarris, which has some superb holes, very linksy.
Walton did St. Helen's Bay, which is just OK. I don't think he set out to build a world beater, though. Smyth did Seapoint, which has an excellent finish, but an uninteresting start (mainly due to the land he got, I'd imagine). Peter McEvoy has done a good few, but he could be English (not sure).
The latest projects in Ireland have envolved Ballisteros, O'Meara, Montgommery, Norman and Ruddy.