I remember that a report to conference on 'real world' use of Haskell, there was a complaint that performance was impredictable due to Haskell's lazyness by default.

The Haskell, which headlines a 14-race card that features six stakes races (five graded), is scheduled for a 5:45 post, with NBC televising the Haskell and the G2 United Nations from 5 to 6 p.m.