Are you copying files, or just text? Clipboard for text works great. For file clipboard sharing (which I turned off because most of the time I don't want to copy files that way) you just right-click on the target machine in a place that "Paste" is a valid command for that OLE type. When you right-click w/ a file on your clipboard, a little "copying" progress dialog will appear (which is why I turned off the feature) and when it's complete, the Paste command will be active in your context menu. Like I said, most of the time I am doing file copy clipboard operations are on the same system, and I don't like having to wait for the "Copy" dialog to finish. When I have aborted the copy dialog, Multiplicity gets all kinds of messed up.
As for copying text in Word, etc., clipboard sharing works perfectly for me with Ctrl+C and Ctrl+V.