With InstantUpgrade, you can upgrade your WordPress installation to the latest or an arbitrary WordPress version with a single click.
Performing Upgrade…
Checking if WordPress root is writable…
Checking if WordPress files are writable…
Checking if work directory is writable…
Downloading WordPress installation package…
Downloading file http://wordpress.org/latest.zip was successful. Filesize: 976527 bytes.
Extracting WordPress package latest.zip…
Removing old files…
Inserting new files…
Wiping out temporary files…
Running upgrade script of new WordPress version…
Result:
Everything went smooth. Have fun with your new WordPress version!