Phew! In about 10 minutes, I have successfully upgraded all my 7 blogs to the latest WordPress version 2.7 , codename Coltrane.
It will be very crazy if I use FTP to upload the files one by one because there are many files need to be uploaded to the server. Especially when I have many blogs need to be updated. So I used SSH access to extract the WordPress .ZIP file and copy all the latest version files from one temporary folder to my blog folders. It is a lot easier and save a lot of time.