When you launch a program, such as Microsoft Word for example, the program runs in full screen on your iPad. A tab on the right side of the screen gives you controls for Parallels Access including a button to bring up all open applications on your desktop computer (where you can browse open windows for each); a button to quickly go to the launcher; a Settings button; and a button to bring up the iPad keyboard. You can also move the Access controls tab up or down on the screen or swipe it off screen to get it out of the way while you work. To bring it back, swipe from the edge of the screen.
The Settings button lets you do a number of useful things for interacting with your desktop programs. When touch-screen controls and gestures are not enough, an Additional Keys button brings up just the important control keys from your keyboard (such as escape, directional arrows, shift, and control) instead of the whole keyboard. There's also a mouse pointer button that lets you left or right click on items and use the contextual menus just like you would on your desktop computer.
I tried Parallels Access with several different programs, and though it takes some getting used to with the touch-screen controls, all of them worked as they should. For all of you wondering whether you can launch games from your desktop computer, you can, but the slight delay and control limitations (you're not using a mouse, after all) make most games unplayable.
The only problem I encountered with Parallels Access was that it wasn't as responsive as using an actual desktop. This is certainly to be expected, but what it means is that you'll often have to try an action a couple of times to get it to work. Still, to get access to the programs on your desktop is probably worth the trouble.
Overall, Parallels Access is great for using programs from your desktop computer on your iPad. Though it's not quite as responsive as using the real thing, with a little patience, most actions can be completed as though you were using a desktop computer.