I haven't really used iCloud Drive yet since I'm not a fan of putting my documents on the cloud, but I gave in yesterday and dropped my holiday greeting card spreadsheet on to it from my main desktop (MacPro3,1 running latest Yosemite 10.10.x) so that I could pull it up on my laptop (2010 MacBook running Sierra 10.12.x).
Went to MacBook, noticed that the file appeared on iCloud Drive, opened it, satisfied. Computer goes to sleep. A few hours later when I'm NOT on a network, I edit the document with no problems and save the update. For the heck of it, I also duplicated the file (well, had to make it a 2016 named file instead of the older 2015 name) so that now the cloud had 2 files. My iPhone 6S running 10.x promptly told me that I had the files as expected and I could view them in the app. My desktop, however, is still blissfully unaware.
During this whole exercise, the MacPro3,1 was never shut down since it acts as a server for the house. The finder window for the iCloud Drive was left open (assuming perhaps an AirDrop-like "needs to be open" behavior), but the original 2015 file still has its last modified date of Nov 27th instead of the 29th and also doesn't see the newly created "2016" file.
I haven't rebooted the desktop a bit out of stubbornness and really more the idea that not only should this "Just Work" (thanks old Apple campaign), but also curious how long is it going to take for the iCloud driver to figure things out.
How long should this take? Any thoughts WHY this is not getting picked up? Is there a way to force a refresh of the Finder window or at least iCloud to convince this thing to get up to date?
UPDATE 2016-12-02: I had left the window opened for a few days and this morning I noticed that it had finally refreshed at some point. Not sure when, but it did. Based on my observation, it was at a minimum 10 hours later.