Hi, I decided to give them a try and have bought some of them very recently, so I tell you what I did and we'll both learn from the answers of those having KO roses since longer time.

1-I read they do well in humid climates and in the heat. Let's see...

2-every source I found reports continuous blooming. I found that double KOs should have a longer blooming season than KOs.

3-for roses it is best to dig a deep hole (I dig a 2"x2" hole, 3" deep, which is maybe too much but helps burning calories...). Then I fill the hole with good fertile soil/loam. There are many threads about good soil for roses, some are very detailed, but I have seen that in general roses are less picky than supposed. In my opinion (and in my personal experience), a good loam and roses will be happy.

4-I am not sure, as you say you are in a zone 7 but you say to have hot summers. How can it be? I am in a zone 8a, I use china roses in full sun, and I use rugosa roses where they get 4 hours full sun and then shadow (i.e. rest). Personally I love the small pavement rugosas and the large roseraie de l'hay, as they are completely carefree and repeat well.

PS: I have read that KOs become large ball-shaped bushes, like 7"x7", whereas Double KOs tend to remain smaller, like 4"x4".

I would not dig a big hole unless, like scardan, I wanted to burn calories. When we planted KO's in a park with clay soil, we just spaded the whole planting area 10-12" deep with some manure. They have grown like crazy with no care except first-season watering and one fertilizing per year.

Another approach to soil prep is sheet composting. Kill the grass with herbicide or lay down cardboard. Pile the area with layers of grass clippings, seedless weeds, shredded hedge trimmings, shredded fallen leaves, and something rich like coffee grounds or alfalfa. Keep it moist through the summer. Next year, plant in the soil (not the compost) with minimum digging.

KO variations are now available in yellow, light pink, and rose pink. Some other easy roses for your area include Earth Song, Prairie Harvest, Winter Sunset, Quietness, and many older tea, china, and polyantha roses. Roses of these types may be absent from your garden center but can be ordered from nurseries like Roses Unlimited and Chamblee's.

"You say you are in a zone 7 but you say to have hot summers. How can it be? I am in a zone 8a."

Yes, I am in Oklahoma. Rarely do we have a 'mild' summer. From June-Sept, the temps run about 90-110 degrees each day and with winds that blow alot, which drys the soil quicker. We have droughts that sometimes last for a couple months with no rain, with water restrictions sometimes. And the humidity? Well, it gets high enough, that it is akin to walking out into a sauna. The makeup I just put on will melt straight down to my neck. LOL.
That's why I question myself on the choice of growing roses and need some that will handle the wild weather here. Thanks for the replies. More are always welcome.

Hardin, I fully understand you, now. It is precisely so in the city where I work... Well, as you put it, the answer would be no, it's impossible to grow roses there BUT that's not true.
Often one can manage to create a "micro-climate" in the garden thanks to a hedge protecting from the wind, for instance, or thanks to a location with more sun, or more shadow, etc.
Thus, even if you live in climatic zone X with Y% humidity, there can be much variance in your own garden with regards to heat/sun/humidity.
Under these circumstances -and forgive me if it sounds trivial- the best thing is to experiment. Try many different botanical families of roses, until you find what suits your conditions, in each single place of the garden.
I started trying these three to see how they perform... one pavement rugosa, one china rose like sanguinea, and one double knock-out. I am currently testing these three, let's see how we will do...