Given posts are themselves a content type, it's rather confusing talking about Custom Post Types. Calling pages a post type, and posts a post type and then trying to explain to users that posts and pages are different... :S
I notice quite a few plugins have already recognized this confusion, an use the term Custom Content Type instead.
I'd like to see this become the official term in WordPress. Over time that would also mean renaming all functions that refer to post type, and deprecating the older ones.
A big job indeed, but WP is no longer a post-centric blogging system, it is a content management system, and it needs language and naming conventions that reflects that.