It's about finding the ideal size
One of my friends is looking at getting a laptop for desktop replacement, so he wants the works, and isn't so concerned about size.
I've decided that I have enough desktop systems, and for stuff that takes a lot of MHz (Mech CAD, photo/video) even the most expensive laptop can't beat a reasonably priced desktop. So, I went looking for a small, but usable notebook.
And ended up with a SRX-87. It's substantially bigger than your U3, but a lot smaller than almost everything else. And, I don't have to drag a USB keyboard around, although I'll probably carry a mouse around (the built-in trackpad ain't bad, but it's not as good as a mouse).
It's definitely worth the extra money over a NV-70; I just can't imagine web browsing on the NV-70 or other PDA. And, it can run all the software I need to do my job (when I add a USB to serial converter so I can talk to PLC's and such).
I still like having my T-615 PDA, since it is so much smaller than the SRX, but it's a PDA, NOT a "Pocket PC". It serves a different role (for one, it's great to bring into a cleanroom to take notes).
I was never a big Sony fan, and in general still am not, but I have to admit that Sony has done a very nice job with their Vaio laptops and Clie PDA's.
Tony