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For e-commerce most of my clients like it cause it makes it easy to find the place of business and even get driving directions.
For my community-based sites I use them in conjunction with my IP2Location database to verify a person is really from where they claim to be.
If neither of the above applies to you then kindly clarify your question and I'll try to provide a better answer.
For a smaller site, or even for a bigger site that does not change often, my preference is not to use a Google sitemap -- but rather to see if the existing site structure is presenting indexing problems to googlebot. I want to know about and fix that kind of trouble, so I can be confident that the url structure and navigational links are well designed. If a url gets indexed only because of an XML sitemap, then it can be harder to spot this kind of issue.
I basically agree with Ted.
The sitemaps you're referring to have been great for my websites. I added them to one of my sites that wasn't getting crawled properly and within a short time the site now ranks in the top three for all my keywords. It's number one for the most popular search term. Members are now joining faster than I can keep up with them.
On another one of my websites I don't use sitemaps at all but still rank number one for the most popular search terms.
This helps to get your content updated in SERPs.