Overall, the changes are mostly superficial. Even the new Task Bar is simply a twist on the existing Explorer UI model, not to mention a blatant rip-off of the Mac OS X dock. Moreover, none of Windows 7's UI goodness is the result of any architectural changes to the OS. The underpinnings are still clearly based on Vista, which explains why most Vista device drivers and services install without a hitch under Windows 7 M3. Not all Vista drivers behave, however; see the next section for some potential trouble spots.

Otherwise, Windows 7 operates much like Vista. There are subtle visual tweaks here and there, but nothing on the level of the dramatic XP-to-Vista transition. Ironically, Vista users may be more annoyed by the UI changes than users coming from XP. Because the Windows 7 and Vista Aero experiences are so similar, seasoned users of Vista will be more likely to look in the wrong places for common functions. By contrast, XP users won't be burdened with now-outdated Aero navigation skills.

Potential pitfalls: compatibility woes continues

One of the more surprising results of my Windows 7 M3 testing was the number of unexpected compatibility issues that plagued each stage of the process. For example, Daemon Tools, an ISO image-mounting utility that works great under Windows XP and Vista, refused to install under Windows 7. Worse still, when I tried to work around the problem -- by using the Compatibility tab in the MSI file's properties dialog -- I found myself stuck in an endless loop of failed installations and mandatory reboots.

The apparent source of the problem -- an incompatibility between the low-level CD/DVD-ROM simulator driver (SPD version 1.56) and Windows 7 -- was difficult to fathom, considering the kernel composition seemed so similar to Vista's. In fact, when I relayed my experience to some of the Microsoft folks on the show floor of the PDC Partner Pavilion, they were equally puzzled. They also seemed alarmed that Windows 7 was incompatible with anything that ran properly under Vista, a reaction I interpreted as tacit endorsement of my understanding of the Windows 7 kernel.

Unfortunately, that wasn't the end of my compatibility headaches. Running under Windows 7 M3 on a Dell Precision M6400 mobile workstation (review to come), Skype 3.8 would randomly crash without warning. Skype showed no debug dialogs -- it just disappeared. But the worst compatibility issue, and also the most alarming from an architectural standpoint, was with VMware Workstation 6.5.

After installing VMware Workstation on the Dell M6400, I was unable to launch any virtual machines. The VMware UI shell couldn't communicate with the VMware Authorization Service, a problem I eventually worked around by running the shell in Administrator Mode. But this "fix" came at a price: the loss of drag and drop between Windows 7 and the VMware guest OS.

Nor was this the only issue I encountered with VMware Workstation. It seems that the VMware Bridge Protocol -- another of those Vista-compatible device drivers you would expect to work unmodified under Windows 7 -- was nonfunctional, rendering VMware's bridged networking mode useless. (In VMware Workstation, bridged networking is the virtual network configuration that allows the guest OS to communicate with the host OS.)