I did the express check in when we went in February, upon arrive there was no difference from what we had to do as opposed to the others arriving at the same time. Although some did get bumped the first night. So it may help with that.
We did the express check in last Dec. We didn't have to fill out any info forms. They were all printed in advance. Couldn't really tell if it made any other difference.
We did the express check at about the 15 day point(31 Mar). Got a nice email with a confirmation number of 997. That number is a new number that is different than any other number in our folder. Email said "This will ensure your room and paper work will be ready, so you can start your Temptation resorts , Cancun vacation sooner".
If they can accomodate you they will, I think that they probably end up getting an organized folder from management every day with rooms etc already assigned so the staff probably doesn't know the difference between an express and regular check in. Don't get too worried, all of the rooms are in short walking distance to the sexy pool and Paty O's!
Keeping Fingers Crossed I called today and they said they have record of our reservation. I hope this is a good thing
