I know that this is often a topic on the flower board so I thought I'd pass along my experience (and some pics).
I ordered the 20 piece white rose package for $399. Get them delivered 2 days before your wedding, and order them 30 days in advance. I ordered them 25 days ahead of the wedding, and got them, but they prefer 30 days. I followed all the instructions, put the bouts and corsages in the fridge, the bouquets and centerpieces in vases with water and put them in my basement which was cool. I checked them daily, they were fine. They will also allow you to change the order around for the right amount of BM bouquets and centerpieces. The only thing they won't do is change the total number of bouts and corsages. We didn't need all the corsages, but I gave one to the violinist and the soloist.
I also found out from the local Costco customer service desk that they have a florist who arranges the flowers in the kiosk. They gave me her number. I felt like a drug addict with a "secret source", LOL. I called her about 2 weeks before the wedding and ordered 70 stems of white Asiatic lillies (way too much), 8 dozen white vendella roses (the right amount) and 4 "packs" of baby's breath. This was about $170, but since I had a Costco American Express card and earned points with work travel, it only cost me $20. I picked these up 3 days before the wedding because the lillies need time to open up. All these flowers were perfect. I felt better being able to see them before I paid for them, versus ordering online, but I'm sure that is fine too. The green "floppy grass" (don't know what it's called) came with the lillies.
Close up of the bouquet flowers that the photographer took:
My bouquet and BM bouquets
White vendella roses and baby's breath I ordered from the local Costco floral kiosk "arranger" and arranged myself.
White asiatic lillies I ordered from the local Costco floral contact and arranged myself with baby's breath:
The flowers were PERFECT!!! I highly recommend doing this if you want, because every review for the rose packages is 4.5 to 5 stars.