Taken from : http://www.macnn.com/reviews/air-display-for-ipad.html
Air Display for iPad
June 23rd, 2010Innovative way to connect iPad as a second monitor for your Mac.
Avatron Air Display lets you use your iPad as an extra monitor on your Mac. It convinces your Mac that it has another monitor attached, and sends the contents of the screen to the iPad over your Wi-Fi network. You can drag windows from your main screen to the iPad and vice-versa.
One of the more unusual applications for the iPad is the Avatron Air Display. This software lets you use your iPad as an extra monitor on your Mac. It convinces your Mac that it has another monitor attached, and then sends the contents of the screen to the iPad over your Wi-Fi network. You can drag windows from your main screen to the iPad, and vice-versa. You can also use the touch-screen on the iPad to click and drag, with some limitations.
If you have a machine with a small screen, such as a 13" MacBook or MacBook Air, the extra 1024 x 768 pixels on the iPad screen can be a huge help. You can use the iPad in portrait or landscape mode and can change your mind any time you want, just by rotating the iPad. Your Macintosh will notice that the screen has changed size and react accordingly.
Air Display Graphic
First, you must install a free driver on your Macintosh, which adds a menu item to the right side of your menu bar. When you want to use the iPad as an extra screen, you run the Air Display application on the iPad. Next, you choose your iPad or iPads from the menu on your Mac, and boom–you have an extra screen.
Macintosh Air Display Menu
The extra screen real estate helps you work more effectively. For example, f you use software that has many small utility windows or palettes, such as Photoshop, you might want to position those windows on the iPad screen. This leaves your main screen uncluttered for working on your image. On the other hand, you might want to put background applications such as a Twitter client or iChat on the iPad screen, where you can check on them with a glance without worrying about covering them up by other windows.
What makes the Air Display unique as a monitor is that it is wireless, which means there are no cables connecting it to your Mac. While this may not sound like a big deal, it is, and it is convenient. You can pick up the monitor and carry it around! I used Air Display during a teleconference in which I had to watch a presentation, but needed to leave the room to get something from another person’s office. I dragged the window onto the iPad, picked up the iPad, and walked down the hall without missing a beat of the presentation.
I discovered some drawbacks while using the wireless touchable screen. I haven't figured out how to move the mouse on the iPad without clicking or having the mouse button down, i.e., touching the screen and dragging. This means that when you want to move the mouse you can touch where the cursor resides and move it somewhere, but for example, if the mouse hovers over an icon in the Dock that drags the icon out of the Dock. Of course, the mouse and trackpad on the Macintosh works just fine. Also, it would be nice if there were some way to bring up the iPad keyboard for quick bits of typing while carrying the iPad around.
I played some movies on the iPad, which is pretty much a worst-case scenario for the Air Display. The wireless link is not very fast compared to a wired connection and a movie requires transferring a lot of data. Apple’s DVD player app would not let me drag the movie onto the iPad screen; when I released it, it slid back to the main screen. When I set the displays to mirrored, the movie played on both screens, but the video on the iPad was jittery. I would not want to watch an entire movie this way. Avatron says that they are working on ways to improve this in a future version.
Easy and Clever
The Air Display delivers a clever way of temporarily increasing the screen real estate of your Mac without buying any additional hardware. I found it useful when I was on the road, and for occasional use in the office. However, if you need more screen space on a regular basis at your desk, I recommend that you buy an external monitor.
You can download the Macintosh side of Air Display for no charge from the Avatron site, but make sure you download the correct Mac version because Leopard and Snow Leopard each have their own download. The iPad portion is available for $9.99 from the iTunes store. It requires 10.5.8 or higher on the Mac and iPhone OS 3.2 on the iPad,
Edited by Ilene Hoffman, Reviews Editor
Easy to set up and use.
Useful when you need more screen space.
Not suitable for watching lengthy videos.
Mouse may move things accidentally.