The standard instructions tell you to use ftp to install and upgrade. I find rsync a lot quicker.
What I do is:
1) backup and turn off plugins.
2) download and unzip wordpress
3) open a terminal, change directory to one level above the wordpress directory.
4) type something like:
rsync -avz wordpress/ firstname.lastname@example.org:/httpdocs/wordpress
5) run upgrade.php and turn plugins back on.
This is a lot faster than using FTP. rsync will upgrade the files that have changed and leave everything else alone.
Linux and MacOS usually have rsync installed, and it is a free download for Windows.
It does require a host that allows SSH access, but even the restricted ssh logins are enough - e.g. if SFTP works, then this should.
Is there anything wrong with this? As far as I can see it is much easier, safer and faster than FTP. The codex currently makes no mention of rsync except a passing mention in a draft article about security. Is there a reason for the omission or should I (or someone) add instructions?