The number one feature I would like to see in WordPress is an easy way to upgrade a very old WordPress such as 2.0.2 or even 1.0 to the latest and greatest WP. I have one blog that is very old. I maintain it for historical purposes - it's an informational blog. Not commercial so there's no money to put in the effort of the difficult path to upgrade to 3.4.1. If there were an easy way to upgrade WP2.0.2 to 3.4.1 I would do it in a minute. But that is about how long it needs to take.