Our recent experience:
I ordered our Fantasmic tickets for May 29 thru Vacation Planning , and our check in date for the Villas at Grand Californian was May 23. When we checked in at the hotel, there was a small pink envelope with Tinkerbell on the front that had Fantasmic typed on the outside. Inside were our tickets and the receipt for our purchase.
We had spent the week at DL and did everything we wanted, so on Saturday, the main focus was Fantasmic. Having never seen it and not knowing when we would be back, I didn't want to miss a thing. We had checked out of the hotel on Friday and were staying with my son, so we drove in late Saturday afternoon. The parking deck was full, so we had to park at DTD. We had enough time for them to do a few things, but I wanted to make sure we had the opportunity to get the seats we wanted, and I was willing to wait in line for this. I made my way over to between Pirates and Haunted Mansion around 6:00 and the CM's with the yellow Fantasmic shirts (crowd control) were already out milling about.
Let me also mention that Guests were already spreading their blankets, and staking out their space to sit on the concrete for the 9:00 show, and this was around 5:40.
I found a perch on one of the low brick walls and watched as they roped off the areas for Fantasmic, brought out the chairs and set up the podium for check-in. Around 6:20, I saw a CM standing at the metal podium talking to a Guest, so I walked on over. He was explaining to her that check-in would be at 8:00 but that a line would be forming shortly to wait for the check-in and that both shows were sold out. She decided to come back later and I decided to wait, making me first in line

. My DH showed up shortly thereafter and we just decided to switch off waiting in line. They had a seating chart there and did not mind showing it to us before check-in, and we were able to actually look at the seats and the chart and decide what we wanted. Around 6:40 the line started growing and continued to grow as time passed.
For anyone else new to this process, I was concerned about finding the check-in spot, but it will be very obvious due to the area being roped off and their being a podium with a light on it.
Around 7:50 they started checking us in. While I think the process is convuluted, and while the CM's think the process is convuluted and have asked for something different, it is what it is. Standing in line and visiting with other Guests was fine and worked for us as we had nothing else we needed to do, except eat some dinner. Once we got checked in and selected our seats (be sure and have your tickets because they do not have a list of who should be there), we went to the Riverview Terrace and grabbed some dinner. They told us to come back around 8:30 for the 9:00 show, so we were pressed for time while eating. It would have been better if we had gotten something to eat before we checked in.
As soon as we were seated, the CM offered us our dessert tray and something to drink, and she was very attentive in refilling everyone's drinks throughout the show. She could not have been any more accommodating and told us we could stay for the fireworks after Fantasmic. We did stay and were able to see them fine, including Dumbo and Tinkerbell flying. Not the ideal angle, but since we didn't have to move, and we had a chair to sit in, it was fine with us. We will see those fireworks from in front of the castle another time.
Fantasmic was really great, the seats were great, the food was great, and to me, it was well worth the money and the wait in line for this night. The crowds were huge (last weekend for Southern Cal passes and first weekend of Fantasmic in months), but the CM's did a great job of keeping everyone seated, keeping the walkways clear and herding everyone in a one-way direction once Fantasmic and the fireworks were over.
Would I do it again, probably, including the waiting in line. Would I wait in line to check in if this were one of my few days at DL, not so sure.
Hope this helps someone else that is new to the process.