I find it tough to rate Ronan O'Gara. I think as an attacking force he offers about as much as the aforementioned Muller Rice.
But there is two things he does right:
1) He must have had his legs tied as a child because the time he practices kicking out of hand is apprently phenomenal - and it wet weather he appears to have got it right and
2) He keeps things simple. Chris Malone at Bath didn't have an attacking bone in his body (nor a defensive one apparently) but he kept things simple, leaving Barkley and Berne to create things, and we had some of our best wins. It won't always cut it but having a FH who can releive pressure and centres who create things makes it a different defensive prospect.
Having said that I think the entire Ireland backline (with the excpetion of Hickey and D'Arcy) are overrated. That includes O'Driscoll (I can hear the moaning already) who has offered no glimpses of his phenomenol ability since the NZ (cheats?) got him. I think Ireland have realistically about as much chance as winning this world cup as England.