For my personal usage habits, I can easily write significant amounts of emails with a stylus, which I do nowadays, but the problem is that any PDA or Zaurus or non-laptop device will not be able to run specific software that I may need (e.g. Scientific Workplace, Latex -may be possible on Zaurus?-, IDL programming language, etc...). Of course, most people use Word/Excel, and there are \'compatible\' devices, but absolutely no software to help me write a scientific article with greek letters and horrendous equations.. which is why I suddenly find something like the U70 quite attractive: a PDA+laptop (standard price combo), or a Zaurus+laptop (expensive combo), or UPC on its own (medium price).
I understand that you are concerned about the price. Still, I\'m convinced that such a hybrid device can\'t really replace neither a PDA nor a Laptop. You will miss the best parts of both worlds: the huge screen of a \"real\" laptop and the \"pocketability\" of a PDA.
My Laptop has a very good battery life, and it\'s \"instant on\", because I reboot it only when I try out a new kernel config, but I don\'t carry it around all day and it doesn\'t wake up to remind me of meetings and stuff.
In fact, I used to have a subnotebook for greater portability, but I changed it for a T40p with a 1400x1050 res on 14\" display, as I\'m note forced to have it with me all the time, because I have my Zaurus. So I now I can enjoy a much nicer screen for the \"real work\" and can use my Zaurus for inbetween (btw. some scientific stuff like R is possible on the Z).
If you are as good with the stylus as you claim (but still: a keyboard IS a nice thing on a PDA) then maybe a smaller and lighter U70 with an external display in addition to the external keyboard for your desk would be a nice solution. But with 550g I would be too lazy to carry it around all day and the price would go up significantly. Plus you would be \"chained\" to your desk for some serious work (and I sometimes prefer other places...)
Seems like there isn\'t a cheap perfect solution, but as the Zaurus is close to perfect, you could use it for a long long time ;-)
Hope, this helps,
cheers Kathrin