I have been putting off upgrading to WordPress 2.7.1 until I could devote a good block of time to the job, but I just upgraded easily. It was easy, no bugs surfaced, and there were no issues to resolve. I should have tackled this sooner. The Dashboard is quite different, but very intuitive to use. The WordPress upgrade was necessary in order to upgrade to the new version of my theme, Thesis 1.4.2. Now over February school break I plan to learn how to customize the theme a little bit, changing the color of the background of the page and adding a header image. I hope customizing is as easy as upgrading!
I recommend WordPress and Thesis both. Thesis is a really versatile theme and I like the style.

WordPress: http://wordpress.org/
Thesis Theme for WordPress: http://diythemes.com/thesis/