My family and I have used room service on several occasions, and here was our most recent experiences:
April 28th @ BC:
It was check out day and we wanted a hardy breakfast. We opted for a meal that fed 4 adults: scrambled eggs, bacon, sausage, pancakes, Mickey waffles, a big bowl of fruit, water, OJ, and coffee. I called the night before (8 pm); the CM taking the order asked, "tea or coffee, and for how many?". Next, she asked me a preferred delivery time...I said 8 am, to which she replied, "We delivery in blocks of time; would you prefer 7:30-8 am or 8-8:30 am?".
That morning came and we got a call from a CM stating that the kitchen was backed up and it would closer to 8:30 am. 8:30 came and went, and right as I was about to call down to find out how much longer, the phone rang: our food and server would be up in 15 min.. Our server, a talkative, super friendly Englishman, apologized profusely for the delay. He was very professional, set up the food, and showed us everything he brought in. Breakfast was good, but too much food for us.
June 7th @ BWV:
I hadn't been feeling well and decided to order in dinner for our family. I called at 5:30 pm and ordered a burger, turkey BLT, and 2 kid's grilled cheeses. The CM told me it would only be 30 min., but only 20 min. passed and there was a knock at that door. CM came in, set up the food, showed me what was delivered and left with a nice tip, even with the automatic 18% gratuity tacked onto the bill.
June 9th @ same place:
We were going to have our pictures taken at 9 am at EP, so I wanted my family to have a good breakfast. I called at 11 pm the night before, and placed an order similar to the one we had at BC. This time, I picked a 7-7:30 am block. The CM asked me if I wanted the server to call before delivery, to which I said, "sure.". Food was delivered by 7:30 am, and the server once again set everything up and showed us what had been delivered.
All in all, room service is nice, convenient, and expensive (double tipping adds up). You can place an order up until 12 am and as early as 6 am. If you want your food close to your desired time, pick the earlier time block. If on the DDP, 2 TS points per meal are taken, as someone has already stated. Room service really makes you feel like you're on vacation!
For our breakfasts, it was for no other reason than do a big breakfast in our jammies then nibble our way thru WS during Food and Wine. A couple of times for lunch and dinner, it was usually due to downpours/thunderstorms. A nice, relaxing night, then up early, rested and happy 
