The new version is of course available free of charge to people who have already purchased the add-on. Check the BlenderMarket page for more details.
WeightLifter add-on: new feature release
Version 20150501170240 adds two new modes: one that assigns values based on the average area of the faces sharing a vertex and another mode that assigns values based on the variance of the lengths of edges that share a vertex. The first one I find useful in creating materials on organic shapes that vary in a subtle but correlated manner while the latter offers a complement to the curvature mode, highlighting certain vertices in a different way. Of course you might find a completely different use for it, that's why I include it in the add-on :-)