We just did this a few weeks ago in February.
On one hand, it was very easy going -- our bags were picked up for us and brought onto the ship, it was easy meeting the transfer, we got to port around 11:30 and were through check-in and on the ship by 12:30. Return was equally as easy, though we waited on the bus for over an hour before it departed.
On the other hand... bags had to be packed and ready for pick up at 7am on the day we were going onto the cruise. My family are not morning people, so this put a bit of a damper on the first day, because everyone was exhausted. When we do a cruise only, we always fly in the day before -- partly in case there are any issues with a flight, but also so my DH& kids don't need to get up early that day.
But the departure wasn't until 9:30am, so we had a lot of time between when we needed our bags to be ready and when we needed to meet the transfer. The bus is apparently no longer themed to Disney (yes, it's been a long time since we've done the transfer) and the time of the cartoons and such they show is shorter than the ride, so we got to know those cartoons and such really well by the time we got to the port. They were also the same shows on the return.
We had to make 2 other stops, so all told it took us about 2.5 hours once we were picked up to get to the port.
On the return, it was really seamless and easy, except they ask you to be off the ship super early and then you sit for a long time on the shuttle before it takes you back to the resorts. We were lucky enough to be the second drop-off, though we hit a lot of traffic so it was a long drive back.
All told -- it IS super convenient, but as a family that is used to doing it ourselves, I think we might do it ourselves going forward at least when it comes to going TO the port. That way we can sleep in during the morning and not worry about having to have bags ready at 7am. You CAN also carry your own bags, and maybe that's what we should have done.