I have used Peggy several times, also Gifts of a Lifetime, and WDW Florist. Peggy was terrific to work with as was Jane at Gifts. The folks at Disney Florist were happy to give me pretty close to what I needed. Of all of them, Peggy was/is the most flexible.
Now....I have yet to have something in the room waiting for us. When I had a box ordered for my dd last June, it was given to her upon check-in. However, the box I had ordered for dh for Father's Day was waiting for him in the room on Father's Day. But, that was 2 days after we got there. When I used GoaL, and Jane, the folks at the S/D seemed to forget that there was a basket to be delivered. It was to be delivered to my friend on her birthday but she got it a day late. Jane made some calls and got it done..the right way. Seems everyone thought that somebody else had taken care of it. And this was 3 days after my friend checked in!!!
With Disney Florist, the basket was held at the front desk and given to the person when he checked in.
I have been told, on several occasions, that they won't put anything in a room until that room has been assigned. And that happens upon check-in. Yes, they have it sort of assigned several days out, but there is a lot of changing around, so the room you were tentitively given by the assigners on Wed, may in fact, be different than the room you actually get when you checkin on Friday. The person who was in your room may have decided to add a day, so you get assigned a different room.
If you really want something put in the room, I would ask that it be held until check in. Then, rather than go right to your room, I would head to the parks or a pool...giving the CMs some leeway in time to get a gift to the room.