It might be useful to generalize [a theorem of Donaldson and Sullivan][1], that the Donaldson invariants are defined for quasi-conformal 4-manifolds, to the category of Seiberg-Witten invariants. More generally, one would like to know which smooth invariants of 4-manifolds are defined for quasi-conformal 4-manifolds. 


  [1]: http://www.ams.org/mathscinet-getitem?mr=1032074