I read otto's post and he does make a good point about custom post types not being for everyone. However, when you're using wordpress as a CMS or have a multi-author site, it's almost a necessity.
Justin Tadlock made a great comment related to this on one of his posts. I can't find it now but it was along the lines of why have posts and pages if pages are really like posts. The same reasoning applies.
edit: found the post. it's in the comment section here
In my case, we regularly create media releases that are formatted exactly the same. Rather than creating a new post and having to remember to fill out custom fields, it would be much better to click on "media release" in the back end and fill out a form.
I find it a shortcoming of wordpress that there isn't an option to include the custom types in feeds without modifying php files or relying on a plugin.
Or what about parent and child posts? I've read some references to these but haven't been able to find an actual example or a way to turn it on. That would remove some of the need for 'series' plugins.
I'm just putting together a separate post asking about how atahualpa handles custom taxonomy. Specifically displaying the taxonomies at the bottom of posts. It looks like I'll have to add a line of php.