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, . (Windows Vista users can opt to install 7 on top of their current OS, although .) 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.

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.)