I had them in front of some Shasta Daisies last year and they totally overwhelmed them. I've dug the Daisies out now, and everything else in there is taller so it should work out ok now. They're in a spot where the soil is kinda crappy, but they don't seem to mind at all, so I'm appreciating the toughness of Calendula :-)
Another new herb for my garden this year is Milk Thistle. Only have one seedling, and it is a pretty thing! I have a feeling one will be plenty- don't want too many thorny plants!