On our last trip, I decided not to do early check in and waited until we arrived. We arrived very early (6:00 am), we were offered a couple of sites which were ready, but they didn’t meet our requests. We opted to wait it out, we ended up in the overflow lot until 2:00pm. That was the longest we ever waited for our site, but maybe we were there at an especially busy time.
I think there are two slightly different issues here.
The first issue is what are the benefits of ONLINE early check-in. The main benefit for Disney is to get your credit card number in advance, run any balance due, and send you a site number if it's ready. If you don't have a site preference or request and have reserved a Premium, for example, you get a site anywhere from 1100 to 400 around/before your estimated arrival time if it's ready (vacant, prepped, clean, blown, etc.). If you are okay with any ol' site, this can get you in "sooner".
The second issue is arriving checking in EARLIER in the morning. This is the route I choose because I have specific sites I would like in 100 (Preferred) or 1500 (Tent) depending on what I booked. I "request" 3 sites as a note on every Fort reservation I make. Sometimes it's pre-assigned but I have to wait for the current guest to leave, wait for it to cleaned, then the system to notify me. I can go 3 more sites deep in each loop if the first 3 aren't available that arrival day which covers me most of the time. However, this requesting/negotiating requires going into the Outpost Lobby anyway. Several times I've arrived before 7am and waited till 1-2pm to get the site number but it was usually one of the ones I wanted - which made the wait worthwhile for me IMO.
Bottom line is I don't do Online Early Check-in since I end up negotiating for a certain site (or site requirement) every time anyway which is fine. But if any site is okay with you, Online doesn't hurt anything and saves you Lobby wait time and conversation if nothing more.
To each his own - I like the early 630am conversations with the Cast Members in the Outpost Lobby. Nobody else is in there but me and them so it's relaxed and easy going and we can do a surprising amount of chit-chat. CM interaction is part of the Fort experience for me.
Bama Ed
PS - the morning shift of CMs start around/before 6am so they are fresh and ready to help.