I live and work in Bangkok, and when travelling to other parts of Thailand on holiday I always take along the Lonely Planet guide. I've tried Rough, Footprint and a few other lesser known publications, but LP tends to more informative, and considerably more accurate, in fact more so than all the others combined.
Another thing, I've been buying each new edition of the LP guide since the early 90s, and can't understand the amazon user reviews dated 1999 or 2002, etc, that identify this guide as the work of Joe Cummings alone. Since the late 90s it has been a team project (with Steven Martin initially, currently with a total of four authors), as any look at the title page or About the Authors page will reveal. So if you don't like the tone, blame the whole team (or more importantly the LP editors, who no doubt play a large role in determining how this book reads), not Cummings!
One thing I did notice about the 2003 edition is that it is considerably shorter than the last couple of editions. Gone are some of the more interesting out-of-the-way destinations in the various regions. I suppose LP felt it had to cut down on the size and weight but I would personally rather see them return to a more comprehensive scope.