I did most of the French side this summer and found it to be spot on. You could be travelling to a town/city by train and reading about your destination, when you get there its totally like the descriptions in the book. Theres lots of background info on Swiss soceity/culture which helps you to chat with the locals by knowing their frame of reference.
If you want a good holiday in Switzerland you have to travel around and see the natural sights, this book is great for planning your itinery.
Only flaw I spotted was I was walking on a bridge in Bern that wasn't on the LP map and was lost for about 2 minutes.
If visiting, its best to buy this before you travel so you can do a day by day plan. I did and it ran very smoothly thanks to the LP guide.