Going from one version to the newest for a software program like WordPress that I rely upon to operate this web site is not necessarily difficult, but it is always a bit safer to work smoothly, orderly and slowly rather than rushing into the dark.
I started by updating all the plugins I use to enhance WordPress. After checking that they were compatible with WP2.1 or that they had a new version compatible with it, I went and downloaded them before installing them one after the other. I could immediately detect an issue with WP-Polls and I invalidated it after a few seconds to secure the quality of the visits (knowing that there us not yet any online polls, it wouldn’t create problems for the visitors).
Then, from a safe situation, I could download WordPress v2.1 and install it separately. Importantly enough, there are plenty of details about how to make a safe upgrade, right in the download page.
Following the instructions was fairly fail-safe and, apart from a minute of file uploading, there was no real impact on the operation.