Bleeding edge is just unfinished.  It generally has all the features of previous versions, but bugs get introduced by changes.  It can be worth it to brave bugs in order to try out specific new features, but then you sacrifice stability.  That's why I have different versions.  So I can try new features without sacrificing the stability of the main version.

I'm not sure how hard it is yet, but as far as I can tell the general task involves to duplicating the seams of mesh a on mesh b as closely as possible, doing a new unwrap on mesh b, then adjusting the UV map b to fit UV map a. That second part is where it's hard to keep distortion low while getting everything to stay in the right place.  

I think that DPH had to push a lot of UV vertices around individually.  Blender has a lot of features I'm hoping will help with that process.  Like pinning, live unwrapping, and minimizing stretch.  The new UV sculpting gives even more general control than proportional editing, along with an equivalent of smoothing.  And the islands to seams feature will make it easier to see V4's seams clearly.  So I think remapping is easier than it was.  Which isn't to say it won't still be hard, just not as hard as it was.