Thanks for spreading the word about the update. With the number of people still running older releases, and the major security holes that continue to be closed in each 2.0.x release, it is very important to get everyone off of the older versions. The two biggest reasons to upgrade to 2.0.5, as I see it, are:
1. This is, again, major security release. There was a major hole plugged;
2. If you started your blog with version 2.0 or newer, you’re missing a DB index on the post table and that will slow down your site.

I’ve provided more detail in a top 5 list on my own site, but you can always look at the official list of all 60 tickets addressed. I use this link to look at it in order of priority.

Please continue to convince your friends and everyone on your blog roll to upgrade, it is important. If any of them are worried about upgrading, I’ve included a 35 second upgrade script on my site. It’s been reviewed by the members of the WP-Hackers list. So, it is safe. I’d post the link here, but I’m releasing an updated version of it later today and don’t want the old links floating around. Just look at the Code Cave article link I posted above and follow it from there. 35 seconds for multiple blogs beats 20 minutes to do it by hand.