  Let $X$ be an oriented 4-manifold which does not have simple SW-type, for
example a blow-up of a rational or ruled surface. We show that any two
cohomologous and deformation equivalent symplectic forms on $X$ are isotopic.
This implies that blow-ups of these manifolds are unique, thus extending work
of Biran. We also establish uniqueness of structure for certain fibered
4-manifolds.
