I've used Lonely Planet guides extensively in paperback and somewhat in Kindle form. The Kindle versions are worse in terms of usability. This is partly because the maps are usable in paper form, where it is easy to flip between the map and the legend, or indeed where they are sometimes on facing pages visible at once. The way they make the electronic versions, the maps often have a low-res overview and legible sections on separate pages. Want to move north on the map? Go forward two pages! That's just silly, a UI worse than MapQuest ten years ago.

What's good about LP on Kindle? If you happen to be travelling very light to several first-world destinations which are not covered in any single book, you can definitely save space and weight. Also if you buy the book more for the prose than the maps, it could be all right (with an iPad and a local SIM card this could work well enough, again assuming you don't travel where people are very poor).