[Haskell-cafe] Stratified monads

I was interested to read David Espinosa's "Stratified Monads" paper at http://www-swiss.ai.mit.edu/~dae/papers/sm.ps.Z I'm not sure I actually understand them properly yet, but I'm already curious about if anybody's played with them in Haskell, or how useful it would be to do so. Any comments? -- Mark