I've been using Desktop Connect on the iPad for these functions, and while it's not perfect, it does have its high points. Desktop Connect will connect to Windows systems with RDP, Linux systems with VNC, and Mac OS X systems as well. There's a very simple interface that shows the remote desktop below an icon bar that allows you to pop up the keyboard and Control, Alt, Shift, and Windows keys, as well as arrows and function keys. Tapping the mouse icon shifts the click from right to left. Desktop Connect also leverages the iPad's multitouch interface to allow pinch zooming of the desktop, so you can size it however you like it.
The mouse support in Desktop Connect has two flavors: normal and touchscreen. Touchscreen is just like it sounds: You tap buttons instead of dragging a mouse around the screen. This method doesn't allow clicking and dragging, however. The traditional mouse control is like using a real mouse, but the tracking leaves much to be desired. It's functional, but takes some getting used to. I wouldn't recommend it for long sessions, but for jumping into Windows boxes to do admin stuff, it's fine.
Both of these apps are very new to the iPad, and they have some bugs, but they're in active development and should get better with time. They're certainly usable now. There are others, too, like WinAdmin and iTap RDP client, though I haven't worked with them.
As far as monitoring goes, I've long been a fan of iStat, which is currently an iPhone app. It runs on the iPad, but doesn't make use of the expanded screen real estate. There's a server-side component that runs on Mac OS X, Linux, FreeBSD, and Solaris, and the iPhone app connects to it, displaying all the pertinent information you could want: load average and network I/O with graphs, memory usage, disk-space usage, uptime, and so on. It's also extremely attractive. Set up a few profiles and you can check on your servers with just a few taps wherever you happen to be.
These tools bring plenty to the table in terms of expanding the usefulness of the iPad for IT folks. In fact, if the iPad supported multitasking, these applications would be much more useful -- it gets really annoying to have to quit and restart SSH and RDP sessions just to answer an IM or check something in a browser. If there's one thing I wish the iPad had, it's that. But as it stands, a single iPad can be your MP3 player, video player, book reader, Web browser, email client, and server administration platform wherever you can get a network connection. It sure beats dragging a laptop around, most of the time.
Now, if we could just get an app that would automatically fix Microsoft Exchange problems...