We just experienced our first after 4pm check-in. I guess I've been spoiled by all the other times we've had room ready, or ready at 1 or 2 pm. We were staying at BLT and checked in at 10:45 am. I had done online check-in too specifying our early arrival. We were moving over from Caribbean Beach, so gave the OL to Bell Services, and then went to the Magic Kingdom for a bit. We came back around 1, room still not ready, so went off-property to Sweet Tomatoes (love that place), came back room still not ready. We were having multiple conversations with Judy, an absolutely sweet greeter in BLT. Got our suitcases and went to the pool. After bingo ended at 4, we were still not in our room. Judy called for us again, and got our studio switched to one that was ready. We had to wait for new keys from the Contemporary. What a treat! We were in 7406, a standard studio with a view of Bay Lake, and the tennis courts straight off the balcony, and Space Mountain and the castle to the left.
I did find myself getting grumpy during the wait, even though I know the other times were pixie-dusted, and these are the rules. I really don't know when our original studio was finally ready, but online check-in didn't overlap with the mousekeeping schedule. I'm hoping we'll be back to our early in-room times next trip, but know the room might not be ready until after 4.