What is a “custom posts feature”? I’m sorry but you will have to expand by telling us exactly what you want to accomplish, or by providing a link to wherever you see “customs posts feature”.
Could it be static page templates that you are referring to? If so then the Version of the Twenty Ten theme we have at WordPress.com has 3: Default; Archives; and Sitemap.
There are two Custom post types in the COM version of Twenty Ten: “Asides” and “Gallery”. When viewing these posts on the front page of your blog, they will display differently than other posts. The way they are effected is by using these as Categories.