I recently found myself needing to update the wordpress software on about 10 blogs I run. After doing the first I thought that there had to be a better way to do this. I found this plugin that does it all for you. Basically you install the plugin and set the permissions on a folder, give it your ftp info and it does everything for you. It is a fast and easy. The best part of it is that when newer versions of wordpress come out you can now upgrade to it with one click of the mouse.
Check it out, if you run a few blogs this thing could save you some serious time.