We always do
First of all it gives something to do during the 60 days leading to the trip, so that's part of the fun
Second you get to pick 2 room requests and this may help even if you've emailed requests. There are also some nice options, for example requesting to prioritize room assignement ( you accept to drop any room request to have the room as soon as possible even before legal check in time) useful if you split stay or arrive early
Third you can specify how early you will arrive and how late you will leave
On a couole of occasions when we were split staying, I mentionned 9am as a check in time and we did get the room that early
Same goes to get bigger chances towards late check out
Fourth you get a separate check in line when you get there, and you can also choose to bypass the check in desk
I understand those who didn't have a nice experience with OLCI, and I understand that it may not save time (tbh on every check in we did we were outside of the lobby while those who arrived at the same time as us were still waiting in line
Anyway, it's free, it's fun, doesn't take time and it may even do some good ... Why not do it then ?