I have never owned one and I was considering buying one. My question is ,does the flower seeds blow off and bring up new seedlings around your yard so you end up with more work than its worth?
Have not noticed numbers of them coming up in garden beds but in recent years individual wild seedlings have been appearing here and there in places where there would be extra moisture such as stream beds and edges of freeways (pavement sheets water off, so when it does rain there is a concentration on the edge of the pavement). Since weed potential seems to be developing in the Seattle area you might wish to not plant this species for that reason, apart from behavior within the garden. In the garden issues that may develop are the large size of the fully developed plants, the size and volume of the spent flower heads and flower stalks, and the tendency for the leaves to be damaged by frosts. (A few years ago some 'Pumila' I had going nicely on Camano Island actually froze almost completely and nearly died, just recently feeble re-growth was noticed). Also the long, arching leaves have razor-like toothed edges. This can be a problem during maintenance operations (including tidying of the plants themselves) as well as simply attempting to pass near the clumps - Pampas grass should never be planted near access routes.