This paper first reviews recent ideas that explain why swirl has a strong stabilizing effect on a flame. Then some measurements are discussed that were obtained using a complex gas turbine fuel injector/mixer operated at realistic levels of swirl and multiple recirculation zones. While swirl is known to have several beneficial effects that improve the mixing and flame stabilization within a gas turbine combustor, swirl also can lead to some undesirable effects. A precessing vortex core can be a source that drives a combustion instability. In addition, swirl affects the unsteady anchoring location of a flame, which also can lead to combustion instabilities, as are observed in our experiment. Interactions between the recirculation zones are observed. The observed large scale unsteady motions cause serious problems for CFD simulations, since the measured mean velocities and turbulence levels on the combustor centerline are much larger than the computed values. Reasons for this difference are associated with unsteady motions.