Note that a lot of the "new" features in WordPress 2.1 are going to seem old hat to users with an account on WordPress.com. That's because most of these features have been available already on that site, and the self-hosted version is just now catching up to the WordPress.com version.
A smooth upgrade
Though I've been running WordPress for years, I ran through the install for 2.1 just to see if anything has changed substantially since the last time I actually installed WordPress (as opposed to upgrading the software). The WordPress installation routine is just about as simple as it gets for self-hosted Web-based software -- download the software, uncompress the archive, create a database, edit the config file, and run through a short Web-based installer.
The WordPress installer worked just fine, and the only noticeable change was that you now have the option of whether you want your blog to be included in Google and Technorati. If you uncheck the box, WordPress won't ping services like Technorati, and it will attempt to block being indexed by Google and other search engines. This is a good thing if you're just maintaining a personal blog and don't want to call attention to it.
After running through the install, I backed up my wordpress directory and MySQL database before upgrading my WordPress 2.0.7 blog.
Again, the upgrade worked just fine. After launching WordPress 2.1 for the first time, all I had to do was to click a button for the upgrade and WordPress took care of the rest. I haven't noticed any glitches or problems after the upgrade, just a handful of new features and performance improvements.
One of the complaints I've had with WordPress is that it occasionally feels laggy when I'm using the admin interface. The public-facing site always seems to load quickly, but sometimes the admin interface seems sluggish. With WordPress 2.1, improvements to the database code have made a marked improvement. Things feel faster when I'm mucking around with the WordPress backend.
Finally! Draft pages
When pages were added in WordPress 1.5, it made it much easier to maintain "about" pages and other static content on a WordPress blog. The only problem? Unlike posts, you could not set pages to be private, nor could you save a draft of a page. This was a bit of a pain in the posterior, because it meant you either had to compose a page outside of WordPress and paste it in when you were happy with the content, compose what might be a lengthy document all in one go, or have a work-in-progress page available for all to see on your blog. That's hardly the elegant blogging experience that most of us had come to expect from WordPress.
I was disappointed when WordPress 2.0 came and went without any improvement in the page situation, but the WordPress folks have finally rectified the problem with WordPress 2.1 and added drafts and the ability to make pages private. You can also set a page as the front page for your site, rather than the actual blog.
There's nothing like spending an hour on a post and then losing everything when the browser crashes or power goes out because you've been so wrapped up in your writing that you've forgotten to save your post at a regular interval. To help those of us who forget to save, the WordPress devs have added an autosave feature. As you're creating posts, WordPress will do a quick save every few minutes, so if catastrophe strikes, you're not likely to lose more than a minute or two's work. Granted, that minute will probably be when you do your best writing ever, but at least you won't need to start from scratch.
Note that autosave doesn't seem to kick in when you're editing posts that have already been published. This is a good thing, since you don't want material turning up live on your site while you're mid-draft.
Import and export
WordPress has long had an import feature for folks moving from different blogging software, such as Movable Type, to WordPress, but it hasn't had any export feature, aside from dumping the MySQL database and reloading it elsewhere.
The 2.1 release includes an XML import/export feature specifically for WordPress. To test it, I created an export from my personal blog, and then imported it into the new blog that I created to test the WordPress installation.
My personal blog has something like three years' worth of posts, which took about a minute to export, and another minute or so for WordPress to slurp up the posts and insert them into the new blog. After importing the posts, WordPress asked if I wanted to create a new user to match the username that I had on my personal blog, or if I wanted to assign the posts to the admin user or another user on the blog. I created a new user, and WordPress warned me that the new user's password would be "changeme," rather than assigning a new password for that user.
One of the things I like about WordPress is that it generates a fairly strong random password when you create the admin user during the install, so I'm not sure why WordPress couldn't do the same for the new user, but that's my only complaint with the import/export feature. Other than that, it seems to work flawlessly. I haven't gone back to read every one of the posts I imported, but I did spot-checking and it seems like it worked just fine.
According to the release notes, WordPress 2.1 is supposed to include spellchecking for posts, but the feature seems to be lacking a bit. While I was able to run a spellcheck, it would run and tell me "no misspellings found" even when I deliberately misspelled words. I'm not sure if that means that the implementation is buggy, or if I'm missing a library or something on my server that WordPress hasn't warned me about. Either way, the spellchecking feature seems to need a little more work before users can depend on it to catch their spelling mistakes.
WordPress 2.1 also adds an upload manager, so you can manage files that have been uploaded to WordPress from a central admin screen rather than trying to manage files via the upload dialog on the post page. Also, the upload dialog has been renovated in 2.1 so it's a bit easier uploading files and including them in a post.
All in all, WordPress 2.1 is a nice update with enough improvements to make it worth the upgrade, especially since it's a low-hassle upgrade that should only take 10 to 15 minutes of your time.