Gooseneck loosestrife is aggressive but its very manageable. Just mow them with a lawnmower and voila...they are in control (at least that has been my experience). They also attract butterflies and bees. If you want a flower garden where every plant is cordoned off from the other flowers within the same bed, then I can see more work involved as you would have to manually remove them. I have to say I know I am in the minority here but I have grown to love gooseneck loosestrife.
Here is an awesome picture I found of gooseneck and beebalm together.
