Dave, I put in a total of five knock outs in February. They are doing well, with a lot of growth and bloom. I am a very big fan of hybrid teas, so not sure if I would add more knockouts; but it is so nice to have beautiful color all summer.

Here is a link that might be useful: My Garden Blog

I am also a big fan of the regular Knockouts and the double ones. I still have the hybrid teas and 5 climbers that I'm not getting rid of anytime soon.

I'm planning to use the Knockouts for mass planting at my church.

believe it or not, KO and DKO are very rare here, very seldom to find in nurseries and to see in gardens. I heard many positive things abouth them, thus decided to give them a try. I have planted 20 DKO (16 red + 4 pink).

For now, they are doing well: no disease, fast growth, they are still very small but always in bloom.

The color of DKO is very bright, and IMO very difficult to combine with other colors. I do not dislike it, but would not mass-plant them (too showy and clear-cut, I prefer more shades of color).
Unfortunately DKOs do not make hips. I am used to rugosas so that's a minus.

Here is a link that might be useful: {{gwi:262917}}