"A good start."4.0 starson by aboardthebebop
Pros: Highly portable, accurate, very impressive to fellow-geeks.
Cons: Only a so-so battery life, getting it to sync was a chore, requires a flat and opaque surface with slightly dimmer-than-normal lighting.
Summary: I got this for Christmas along with a Palm TX and I take them almost everywhere. As mentioned, my only complaints are that it took a while to sync. Seeing my frustration, my friend ended up doing it in about 1 minute... I'm not sure what he did differently, but there are plenty of help sites out there (http://www.compact-impact.com/contents/index.php?option=com_content&task=view&id=31&Itemid=27 or http://www.virtual-laser-keyboard.com/F-A-Q.ASP#a-31 are helpful).
It's still a bit pricey for another toy but if you have a large and heavy laptop you don't like toting around, you may want to consider getting this.