Matthew Mullenweg announced at Wordpress.org that Wordpress 2.1 "Ella" is available for download. Some of the new features and changes listed in this version of Wordpress that I think users will like include:

• Autosave makes sure you never lose a post again. I'm a habitual browser closer before saving my work...so this will be a big one for for me!
• A tabbed editor that allows you to switch between WYSIWYG and code editing instantly while writing a post.
• The lossless XML import and export makes it easy for you to move your content between WordPress blogs.
• You can set any “page” to be the front page of your site, and put the latest posts somewhere else, making it much easier to use WordPress as a content management system.
• Much more efficient database code, faster than previous versions. Domas Mituzas from MySQL went over all our queries with a fine-toothed comb.
• Pages can now be drafts, or private.
• Comment feeds now include all the comments, not just the last 10.
• A new version of the Akismet plugin is bundled.

Developers are also expected to like the cleaner code, API improvements, and a number of other improvements since Wordpress 2.0 was released. Most of these improvements should especially help in Wordpress plugin development.

References:

1. Original Announcement
2. Download Page for Wordpress 2.1 at Wordpress.org