Now TeamViewer HD is not for iPad alone... it works very much like the Real VNC program I used to use to connect to remote desktops. So the concept isn't new, just the ability to do it from the iPad is. As with all remote desktop sharing software, you are literally connecting to the desktop as though you were sitting in front of that PC. So, remember, anyone that happens to actually be in front of that PC (or Mac, or Linux) can see everything you are doing.
The touchscreen capability of the iPad is limited to the moving around of the remote mouse, so you don't get a touchscreen effect on your remote PC (and it can be a little disorienting at first because your finger movements can feel opposite that of how you normally operate the iPad. For example, when you move the mouse down (by dragging your finger), the screen will go up when you reach the bottom. There are a number of options that work with the touchscreen that make the product work well, such as the tapping of two fingers to emulate a right-click. It takes a little getting used to, but you should quickly catch on.
TeamViewer HD is free for personal use, and can range between $719 - $2,690 depending upon your licensing of the product for business purposes. I've found it very, very useful in the few days that I've played around with it. Here are a few screenshots of what the product looks like.
The Login Page
Splash Screen w/Basic Instructions
Navigating Through the Start Menu
Small Screen View w/Keyboard
Landscape View (of me catching my kids watching Justin Bieber Videos!)
A Reminder Screen That I Should Only Use This For Personal Use