I've received enough email about this that it's clear I missed the boat in not mentioning this sooner: With a Patch Tuesday software update that it delivered last week, Microsoft has returned the SkyDrive icon to its rightful place in the system tray and added back the progress animation in File Explorer while SkyDrive-based files are downloaded to your PC.
Can I get an Halleluiah?
Back in the good old days of Windows 7 and Windows 8.0, you had to download a SkyDrive desktop application to add file sync to the PC. This application is pretty full-featured though. It comes with a tray icon that provides you with an at-a-glance view of the health of file sync (if it's white, everything is fine). And if you navigate to the SkyDrive folder in Windows Explorer/File Explorer, you can see the sync status for folders and files marked as being available for offline use.
Then Windows 8.1 came. This release provided integrated SkyDrive file sync capabilities, so there is no more need to find and download that separate application. (Plus, it works with Windows RT, too.) But Windows 8.1's SkyDrive file sync functionality, as originally shipped, was perhaps a bit too Metro-centric. The tray icon and sync status icon overlays were removed from the desktop environment.
Now, they're back (mostly), thanks to an unexpected new software update that you will automatically receive through Windows Update.
The update itself is almost hilariously named as Update improves SkyDrive experience in Windows RT 8.1 and Windows 8.1. Even funnier is its description, which simply states: "this update improves the SkyDrive experience for all users in Windows RT 8.1 and Windows 8.1."
This update provides two of the three SkyDrive sync-related things that were missing in Windows 8.1, the tray icon and the sync status on icons. But what it doesn't add back is the green checkmark overlay indicating that all is well. You only see overlays on file and folder icons while they're syncing.
Incidentally, SkyDrive Pro still provides this functionality. Here's what it looks like:
You can of course see whether files or folders are synced if the view is in Details view; the Availability field will note "Available offline" for files and folders that are synced.
Note: This addition was previously seen in leaked builds of Windows 8.1 Update 1 as well.