The keyboard should work fine, I use it now with my NX80. The IR transmitter is on a movable arm that can swing from a horizontal to a vertical position to line up the IR ports. The arm may not provide enough clearance to enable you to use it with the wireless card installed however. I also initially had some concerns about dropped characters, but after more testing over the past few days it turns out my typing is just a bit sloppy.
As for the caveats, the Clie sits loosely atop a spring bar (barely visible just above the "wireless keyboard" text in the photos), & the keyboard doesn't lock open so you won't be using it on your lap. In addition, you'll most likely need a Symbian driver to be able to use it with the phone. Hopefully, Palm or ThinkOutside will develop drivers for other devices to make the keyboard more versatile.