I have one... assuming when you say laser-projection you mean infrared.
I used to use it with a Treo 650 with mixed results. Biggest issue beyond the problem of keeping both device and keyboard in line-of-sight was that there was a delay between typying the key and seeing the chararcter appear on the screen. Sometimes the character won't appear too (the line-of-sight issue).
I bought a Bluetooth equivalent (it's called "Think Outside Stowaway Ulta-Slim Keyboard") and was really surprised and pleased. So pleased that I put the old infrared keyboard in the closet where it has remained ever since.
The construction quality of the Bluetooth product is excellent (much better than that of the infrared) with a nice leather case for travel. It has a fold out docking port to rest the device upon that actually works. Net effect is that it's just like having a PC with a LCD screen (admittedly much smaller <g>). Heck, it even has customizable shortcut keys!!!
I have to say, I REALLY love this device! I sit in coach on planes and type away. Even when the @%$! in the next seat forward flops their seat all the way back... life is good.
If only Documents2Go would come out with their promised BlackBerry product I would again instantaneously dump the laptop! (I say "again", as I too am a withdrawing Palm addict who got fed up with carrying around 3 extra batteries and planning travel around my batteries' recharge schedule.)