The upside of WordPress is it's free, full featured, fully supported with ongoing development and oodles of plugins to add even more functions and features. The downside is it's computer software that unfortunately needs upgrading and updating at some point: sometimes for feature changes, other times for security risks. Most upgrades on WordPress have a little of both.
WP 2.7 is a big change from 2.5, but it's worth it and is going to be necessary at some point. Eventually older versions just aren't going to function with even the simplest of plugins, and you could be leaving your system open to a security risk with older versions.
I like the wp-automatic upgrade plugin. It truly does work very well. It does all the steps necessary for you to upgrade all from within the wp-admin area. I plan to continue to use this plugin, even though 2.7 has a built-in upgrade feature, because it's built-in feature isn't nearly as good as the plugin.
Check out my blog for my video tutorial on the wp-automatic upgrade plugin, with a link, if you're interested.