I'm using the iPad with the bluetooth keyboard right now to type this, and I've noticed that many of the standard shortcuts from OSX (like command+c for copy, command+a for select all, command+z for undo, etc) work great. You can even use the arrow keys to navigate through the text box you're editing (and even use command+arrow key to jump to the beggining / end of a line and option+arrow key to jump between words. In addition, you can hold down shift and use the arrow keys to select text. Sadly, command+r doesn't refresh in Safari, neigher do the arrow keys allow scrolling the web page. Hopefully these and other shortcuts will show up in iOS 4.0 tomorrow.
In mail, if you click on the title bar above the inbox in landscape view it scrolls the inbox to the top, if you click it above your message it scrolls the message to the top. Nice little touch.
Many people might know this, but Maps has terrain view, which I didn't realize until today.
Holding down the volume down button for almost a second mutes the device. Good to know since there isn't a mute switch (replaced by rotation lock), but kind of annoying for people who want to go from say, full volume to half volume without clicking it 8 times in a row.
The option to keep the bookmark bar always on top is a favorite of mine that some people I've talked to didn't know about.
You can play slideshows from the Photo app over the VGA cord to your HDTV. The fancy origami transition is disabled though for some reason. Actually, come to think of it, I think the only option was dissolve? Not completely sure on that one though since I don't have it hooked up right now and don't feel like messing with it.