This is a great idea! I've lately been making a special effort to rate and review the plugins I use (even trying to make sure I click the Works button), and I keep wishing more people would do the same. It's pretty frustrating when trying to choose between various plugins if there isn't enough data to make that decision... I hope a lot of people participate!

Here's another tip for easily finding plugins... I generally add the plugins I use to my WP.org Favorites list, to make finding them easier even if I'm not on the backend of my site. Plus it gives me a complete list of all plugins I use on all my sites, not just for a particular site. And from there I can see what ratings I've already given and which plugins I haven't rated yet, which makes the task even easier :)