... to accomodate set recurrences like First/Follow, while retaining the flexibility needed to compute monotone map lattices.
See the changes to solveProblem, which now takes a DependencyM graph domain a action instead of a Node. Previously, that meant that you could only effectively return a value of type domain from your problem (through said Node), now it's possible to return arbitrary an arbitrary value of type a that can be computed by accessing any number of Nodes in the graph. You'll get the old API just by calling dependOn on your node to construct the DependencyM action.
Type inference worsened from this change, but it seems like a worthwhile improvement of the API.