First, a display must be firmware-upgradable by the user. I once had a firmware problem with an older, nontouch display, and the only fix was to ship it back to the manufacturer. Ensuring that users can upgrade firmware is a major advantage.
Second, the display's touch digitizer must be HID compliant. HID (human interface device) is the standard for USB input devices. An HID-compliant device won't require a separate driverso once you connect the USB interface, touch should work, with no further device driver installation required.
Various other certification requirements address touch latency, touch separation detection, and more. The only technology that covers all of these bases today is capacitive touch. Other technologies, including infrared sensors, seem promising, but no manufacturer yet ships a display that meets Windows 8 certification while using sensors other than capacitive touch.
Connections and ergonomics
In addition to having USB connections, you'll need display connectors. Most displays ship with DVI and even VGA connectors, but they also typically include HDMI connectors. And some monitors, such as Dell's aforementioned 23-inch S2340T, include DisplayPort connectors.
Product designers are also doing interesting things with stands and ergonomics. The Acer T232HL (shown above) uses a single, curved bar attached via a ratcheted spring mechanism to enable the display to tilt at various angles, depending on how you want to use the hardware.
Dell's S2340T, meanwhile, offers an impressively flexible stand that you can tilt easily at various angles, including completely flat (see below). The USB 3.0 ports are on the base and are easy to reach. The Dell also includes a webcam and an array microphone, which make its $650 price a bit more palatable.
What about support for multiple displays? Well, you probably don't need two or three touch displays, as most of your touch opportunities will occur in single-screen-only Windows 8 apps and in the Windows 8 Start screen. Of course, you can use touch on the Windows 8 desktop, but there it's useful primarily for basic system navigationsuch as for calling up the Charms bar.
I've already mentioned the dearth of high-resolution touch displays, but integrating multitouch in high-resolution monitors is certainly possible. Case in point: Dell already sells a 27-inch all-in-onethe XPS Onethat features a native 2560 by 1440 resolution. Whether future touch displays take this direction will depend largely on consumer demand and on how much consumers are willing to pay. The prices of 27-inch, 2560 by 1440 panels are starting to drop, so I hope that we'll see some high-resolution models with multitouch support by early 2013.
In lieu of a new display
If you're already heavily invested in a high-quality monitor, you can take advantage of the new touch interface in other ways. Microsoft and Logitech offer a line of multitouch-enabled mice, for example. And perhaps even more useful is Logitech's T650 wireless touchpad, which fully supports Windows 8 gestures. As a desktop user, you may not want to give up your mouse for a touchpad, but the T650 makes for an interesting secondary input device.
During conversations with various display manufacturers, I learned that capacitive touch sensors add about $100 to the price of a display. This premium will likely decrease over time. For now, though, if you want a touch-enabled Windows 8 experience on your desktop, you'll have to pay a price premium to get it. Nevertheless, once you start using those new touch gestures, you'll have a hard time going back.