I found the guidebook useless on my Kindle 3 and am asking Amazon to delete it and give me my money back so that I can buy a paper version.
The e-book lacks an index. This means that if you want to look up the entry on Zaragoza, for example, you have to "search the book" - which then brings up every paragraph in the book which mentions the word Zaragoza. I counted 92 entries over 16 pages.
The maps are either tiny or are tiled and aren't really any use.
It had been my intention to use the Kindle rather than lug heavy books along - but with a paper book I can find what I want in seconds; with the e-book I engage in combat with the damned thing for several minutes.
The Kindle is great for reading novels and other narrative - but for a reference book like Lonely Planet, it doesn't really work yet.