Yes, WordPress 2.1 has been out for a few days, and there have been some significant changes. What that means is that your templates and some of your plugins might not work.

So I suggest you wait a few weeks, until other people have worked out the bugs, and updated the templates and plugins.

Meanwhile, if you’re using WordPress 2.0 plus, but missed WordPress 2.0.7 , the last and most secure of the 2.0.7 series, you can download it from the WordPress Release Archives