Version 2.6: WordPress v2.6 gets versioning.
Version/revision saves a copy of a post every time you edit it, allows you to view (not edit) each of those copies (revisions), Shows forward (in time) diffs between any two revisions.
I’m a big fan of versioning. As I discussed in this post, I think it’s a core component of content management, and it’s tough to call a system a true CMS without. This argument managed to persuade Josh Clark, so perhaps Matt Mullenweg read it too?
This is a feature in Drupal as well. Very handy feature, I agree it should be part of any CMS.
The thing that always bothered me about versioning in Drupal is that it's option. Maybe that's not a big deal, but it just bugged me that you could shut it off.
I'm probably being silly.
It could potentially cause a lot of unnecessary (depending on who you ask) database bloat that some administers don't appreciate. That's why I think it's better that it's opt-in rather than opt-out. But really, you can't complain too much so long as the option is available :)