The only time you'll definitely be forced to make adjustments like that is when playing Blu-ray movies. Because of DRM, the Blu-ray video signal will only play on one display at a time, so you'll have to use the Windows display options menu and select the option to use the external display only (as detailed in the video above). Once we had that set up properly, our Blu-ray video played wirelessly on our remote display with no trouble, although the image had a slightly compressed quality, and it wasn't as good as you'd get from plugging a Blu-ray player into the TV's HDMI input.
It's also worth noting that HP's nearly identical version of this technology, called HP Wireless TV Connect, did somehow allow us to view Blu-ray video on both the laptop screen and the external display at the same time.
Our next big test was gaming, as Intel's WiDi imparts just enough lag to make gaming an impossibility. Using the PC version of Mafia II, we were able to launch the game and have it display simultaneously on both the laptop screen and the TV. This is a fast-paced action game, with no leeway for laggy screen response, but playing via a controller plugged into the laptop, we were able to ignore the laptop display and focus entirely on the big-screen TV with no noticeable lag (although the kind of expert gamers who decry wireless mice for their lag over wired models may disagree). In the video above, you'll note that the brightness and contrast settings for the two displays were very different, and we had to choose one to focus on when adjusting the in-game display settings.
Gaming via the WiCast is especially handy if you're looking to play PC-only games such as Starcraft II or Civilization V on a bigger screen without dragging your laptop over to the TV to plug it in directly.
Asus claims that the WiCast will transmit from up to 10 meters away, although walls and other interference can make that very case-specific. We were able to run it from the back end of our lab (about 45 feet) easily, but the signal started to show some blockiness and pixelation after about 15 feet.
If you're looking to wirelessly transmit your laptop signal to another display, both the Asus WiCast and Intel's WiDi have strengths and weaknesses. The WiCast is more flexible, allows for Blu-ray content and gaming, and even works on other devices (we successfully used it to hook up an Xbox 360)--but it also results in a tangle of hardware and wires that makes it less portable. At $199, it's probably best for those with a specific use in mind, but we look forward to the day when we can get the same functionality with either internal or USB-key-size components.
It's also worth noting that there are other PC-to-TV solutions out there. For example, the Warpia Wireless USB PC to TV and the Veebeam HD both use USB dongles instead of a laptop's HDMI output. Wireless HDMI transmitters and receivers have also been around for a while, but previous models have been expensive and aimed more at home theater enthusiasts.