I haven't fished it myself but I have spoken to some people who have and when conditions are right it has great spent mayfly fishing for huge trout. Early season it can be fished with wet fly in the shallows. Large dabblers and fry imitations.
The article in TandS was by Dennis Moss and he had a nice fish (3ib?) on mayfly dun pattern as far as i can remember. He recommended the lake for those who want to get away from the crowds.
There has never been any doubt as to Ree holding large numbers of trout , however they concentrate on the coarse fish for their food as far as I know and thats not every fly mans cup of tea.
Beware it is one of irelands widest unbroken stretch of water and when the wind gets up from the west (as it usually does) it can develop huge waves. Its also knicknamed "rock ree" I'll let you work that out for yourself

. Best of luck I've always wanted to fish it but never got round to it.