WordPress 2.2.1 is now available…
You can read the rest of the post for the details. I ran Winmerge against the new version and the old version. It showed that 40 files are changed and two files were added. It looks like an upgrade that lends itself to upgrading just the changed files. I have an interest in the changed files since I keep my websites in a Subversion repository.
In the past Mark on WordPress posted a zipped version of just the changed files but he appears to be busy with some personal issues like a new job and a wife. I actually used Winmerge to create a zipped file of just the changed files to see if it would work. It did. Mark had a different procedure. I may modify my upgrade procedure to use a zipped file after I do a little testing.