Version 2.1 of the WordPress blog platform was released earlier this week. General reaction in the blogosphere has been highly positive.

This new WordPress version comes with over 550 bug fixes and some significant changes behind the scenes in, for example, how some of the code works. This will have a major impact on a number of existing plugins, some of which just won’t work with WP 2.1. If you’re thinking of upgrading, check the plugin compatibility list first.

The list of improvements and new features is lengthy. Here’s an extract of those I find especially appealing:

• Autosave makes sure you never lose a post again – useful if you write your posts with the WP online editor.
• The new tabbed editor allows you to switch between WYSIWYG and code editing instantly while writing a post.
• The editor now includes spell checking.
• New search engine privacy option allows you to indicate your blog shouldn’t ping or be indexed by search engines like Google.
• 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.
• Links in your blogroll now support sub-categories and you can add categories on the fly.
• More AJAX to make custom fields, moderation, deletions, and more all faster.
• Pages can now be drafts, or private.
• Comment feeds now include all the comments, not just the last 10.
• Better internationalization and support for right-to-left languages.
• The upload manager lets you easily manage all your uploads pictures, video, and audio.
• A new version of the Akismet anti-spam plugin is bundled.

So, should you upgrade from a previous version?

The answer has to be yes from the bug-fixing point of view alone, especially as some further security issues were addressed in this new release.

It’s also a yes if you want to take advantage of the cool new features and functionality.

But this is not a casual upgrade. Not only are there some plugin issues as I mentioned earlier, there’s also a change in the versions of MySQL supported by WordPress 2.1 which supports only MySQL 4.0 or greater – support for earlier versions has been dropped with this release.

If you don’t know which version of MySQL your current WordPress blog runs with, I recommend a very handy plugin called Diagnosis which presents tons of useful information about blog and your server including the MySQL version installed. The latest version of Diagnosis will work with WP 2.1.

I plan to upgrade to 2.1 but on my sandbox blog first, not here in this blog. I have to resolve issues with the theme I use here (a modded K2) as commentary in the K2 forum clearly indicates K2 will have problems with WP 2.1. Plus I want to play with all the features before committing a change here.

So time for experimenting soon.

And, by the way, today is WordPress’ fourth birthday. Many happy returns!

[Update @ 21:06] Fear not WordPress 2.1 and WordPress plugins, says Lorelle VanFossen in an excellent post packed wth tips and advice on upgrading.