Whilst i am a definite advocate of pilots discretion in this area, and fortunately for me, my company allows some discretion in the use of autobrake, mainly that it is only mandatory on slippery runways, however i take on board the comments about landing on ice at Kef. That is something i have not yet tried on an auto brake equipped A/C.
Having said all that, no matter how much money you save on brake wear, one visit to the golf course undoes all that good work, and then some. I know there was a lot of other factors in that small glitch in an otherwise perfect safety record, but it is likely that a logical autobrake selection (probably 3 or 4 given a wet runway) may and i repeat, may have saved the day. So it is fairly hard to argue against the use of autobrake on carbon fibre units. Steel brakes are a different matter as 18 wheeler points out. Turn around times and wear are can be significantly affected by judicious application of brakes around 80kts.