I used them, I had them delivered two days before my wedding so they would open up right on time, I arranged them in my house (but you need a lot of supplies and space for this if you're DIYing the arrangements) and stored them in the basement to keep them cold.
I have gone back and forth on what I want for flowers. I was considering to go with a Toronto florist just for the wedding party and parent’s flowers. Since it costs a lot of money, I am considering getting flowers from Costco for just the centrepieces. I know more greenery can balance the price. They do have greenery runners for tables at Costco. Again, I’m not sure about the quality.
My sister and sister in law used Costco florals. You place your order in advance so that they ensure you get quality florals at the right time (you may already know this but in response to below). They were both SOOO happy. They were beautiful (mind you they didn't get the premade arrangements; they ordered the florals and greenery and had someone they know put them together. I should add, my sister's wedding was 20 years ago and my SILs was 3 years ago. Both were very impressed. I still have my bouquet (dried) from 20 years ago 😂😂😂.
The thing with Costco, like any other grocery store flower section, is that you're at the mercy of what they have at the time and you have to go get it yourself on the day of. Some people try to get it the day before but the fact is, we don't have the equipment to keep flowers fresh and fully bloomed for a long period of time.
If you don't have much flowers planned (bouquets only and no decor or centerpieces) and flowers overall are not a big deal for you (you're not obsessed with the arrangement and look), then it should be fine though I recommend getting it the day of instead of the day before for reasons mentioned above.