This site was upgraded to WordPress 2.7.1 without any problem. It took me about 15 minutes to complete the entire upgrade process, which included downloading the latest source file and backup the existing files.
I noticed the admin layout was different from the previous version 2.6 that I had. It took me a while to familiarize with the new layout.
Several plugins had newer version. I upgraded them with the upgrade automatically feature. Everything is working as it is suppose to be. What a relieve!