Do you think I need the system I have to write prose?
no, but you may well need a full sized keyboard. I myself wouldnt ever use a netbook as my daily driver even though all I do is write prose and check email for the most part. The biggest reasons are:
a) I would really appreciate a full sized normal keyboard when writing for 10 hours a day
b) I would really appreciate a screen size larger than 8" or 10" when writing 10 hours a day
c) I have a TON of "helper programs" that launch on bootup, and I need them all to run fast and snappily, ie, so even if i'm writing prose all the programs in the background would not run as smoothly as I'd like if they werent on a core 2 duo at least running at 1.8ghz with 2 or 4 gb of memory.
d) I multitask like crazy: at any given moment while doing research I have about 20 browser windows, surfulater, onenote, evernote, a half dozen word documents, Endnote, all open and running. No way a netbook will handle that with ANY grace.
e) On top of the above, I often watch videos, movies, and even play the occasional round of battlefield.
f) So how much weight and space does a netbook save anyway? I have a 14" laptop which weighs only 4 pounds and is TINY ENOUGH already. And has a battery that lasts 5 hours.
So in short, even though I do think netbooks are "neat", there is no realistic way its going to replace my 14" fully functional laptop even for "spontaneous" uses, or even for prose writing. As I understand it the 14" laptops coming out in the next year will be even lighter, have batteries that last even longer, and will be even thinner.