HomeGroups are disappointing: HomeGroups sound like a nifty idea--a way to share folders full of media and documents between PCs across a network, so you can peruse photos stored on a desktop in the den from your laptop in the living room, for instance. But Microsoft's implementation is surprisingly half-baked: Rather than letting you specify a password during setup, for instance, it assigns one consisting of ten alphanumeric gibberish characters and tells you to write it down. And HomeGroups work only if all the PCs in question run Windows 7. A version that also worked on XP, Vista, and--dare I say it?--Macs would have been far cooler.
Windows Update can still shut you down: There's no reason to believe that Windows 7 will require less patching than earlier versions of the OS. If you use Windows Update the way Microsoft recommends, however, your computer may still demand that you shut it down so it can update itself, or it may decide to devote an extended amount of time to installing updates when you try to reboot it. In the largely compliant and considerate Win 7, this aggressive approach to updates is a flashback to Windows' pushy past.
You can't upgrade Windows XP: If you want to upgrade a PC from XP to 7, you'll need to start anew, reinstalling all of your apps and re-creating your settings. (Windows Vista users can opt to install 7 on top of their current OS, although not in every possible scenario.) Microsoft's decision not to enable XP-to-7 upgrades is defensible--a fresh install will probably be more reliable than one plunked down on top of XP's eight-year-old underpinnings--but it will scare off some XP users who would probably love Windows 7 once they got it up and running.
...and the Unknown
How bad will compatibility issues be? Windows 7 looks and works differently than Windows Vista does, but below the surface it isn't radically different. That should make for fewer headaches with incompatible drivers and software--and indeed, it helped even the earliest Windows 7 preview versions run surprisingly smoothly for prerelease operating systems. But as millions of people install Windows 7 on an endless array of PCs, undoubtedly some of them will encounter problems that Microsoft didn't anticipate. (I've run into setup quirks and driver issues with the Windows 7 RTM version myself, but I've been able to work around them--by installing from a USB drive rather than a DVD, for instance.)
Will hardware companies take to Device Stage? This new feature gives your printer, camera, and other peripherals information centers of their own, which hardware manufacturers can customize with features such as links to online manuals and troubleshooting tools. But unless companies invest the time to build useful Device Stages, this could be another Microsoft bright idea that doesn't go much of anywhere. Also, parts of Device Stage look short on substance (giant photorealistic renderings of your peripherals!) and others look potentially irritating (printer companies hawking ink cartridges right inside your OS!). All in all, I don't think it'll be a tragedy if Device Stage doesn't catch on.
Is touch input a boon or a boondoggle? Windows 7 is the first version of the OS with special support for multitouch input--for example, if it notices that you've opened the Start menu with your finger rather than the mouse pointer, you'll see a roomier version of the menu that takes less precision to navigate. Of course, all of that requires a multitouch-capable PC, and only a handful (such as the upscale HP TouchSmart) are on the market. Windows 7's arrival might prompt a profusion of interesting new touch-enabled PCs--but even then, what we really need are interesting touch-enabled applications. (Microsoft's touch demos have tended to feature such ho-hum uses as fingerpainting in Windows' own Paint program.)
The Bottom Line
Last year Microsoft tried to repair Windows Vista's reputation by pretending it was a new OS code-named Mojave and getting focus-group subjects to say nice things about it. If the company had released a Vista back in 2007 that was as pleasant to use as Windows 7 is, the OS might never have had image problems in the first place.
Even when an OS upgrade is as appealing as this one, it makes sense to proceed with caution. Many of the people who grab Windows 7 at the first possible opportunity will be happy they did. But I suspect that some of the folks who wait a bit more--installing the new OS only after other people have discovered unexpected glitches with applications and drivers--will be even happier. And if you're using an aging PC, it's perfectly sensible to hold off on Windows 7 until you're ready to buy a brand-new system that's designed to run it well.
My advice for Windows users, then, is this: Get Windows 7, but on your own schedule. It'll be ready when you are--and you'll almost certainly consider it an improvement over whatever version of Windows you're using now.
Former PC World editor Harry McCracken blogs at his own site, Technologizer.