That is about it for the content, believe it or not; it is direct and straightforward without any fluff or nonsense. You are simply covering each detail so the seller knows exactly what the buyer intends to do. Having an informal letter of intent also allows for easy negotiations.
There are enough litigation examples on this issue around to suggest their fears are well placed. A confidentiality agreement (also called a non_disclosure agreement) and followed by a letter of intent is the two step process for allowing a business concept owner to establish a new business relationship without losing control of their business idea.