As of PureScript 0.12 the default type for handling effects is Effect from purescript-effect. This differs from Eff by removing the row of effect types. This decision was made as getting the effect rows to line up was sometimes quite tricky, without providing a great deal of benefit.
There is also purescript-run now, which uses a similar effect row mechanic but provides true algebraic effect handling.
The previous releases will continue to work for older libraries that still depend on them.