Get a pda? and a pdf version of the books, I'm sure there are plenty of versions.
Possibly, but a book is, overall, cheaper, more damage resistant and easier to use / lend to people. Plus I like going to places where electricity may not be available (although this is less of an issue with solar charger).
Thing is trusting books can be dangerous, you should never assume.
Anyone dumb enough to assume that a book, or any other source of info, is 100% correct deserves to have problems. However, a book or any other source of information is a good start and if it's wrong there is usually other infromation to help you out (such as the location of local internet cafes!).
I guess I just prefer books as that's what I've used whenver I've been travelling. I too have an archos, but the only thing I use it for when travelling is watching films on long-haul, I certainly wouldn't entrust my planning info to it.
Also, one book per country isn't that big or heavy, particularly when compared to an archos and charger. How big a rucksack are you taking? You'll probably need a reasonable amount of gear for NZ and OZ, but for Rio and SE Asia, hand luggage should suffice.