I have no idea whether the IP changes or not, since I usually don't have the unit on when I'm walking around.
My iPaq is the h4155 and can be found in HP's high ed student/faculty store
here (bottom of the page) for $400. You can also find it in the City of Industry Fry's (they put up a demo unit) and West Covina Circuit City for $449.
BTW, I had no problem with the wifi network inside the library today. I spent about an hour on the second floor around noon time.
Oh, I saw a new Sony V505 at Fry's with Centrino, but it's in the $1800-$2000 range.