I certainly agree with Traci about keeping plugins to a minimum, but, personally, I consider Joost de Valk's fine Google Analytics plugin (mentioned earlier by tracyr) one of that minimum. Joost is one of world authorities on WordPress and does a good job of keeping his plugins up. I especially like his guide to WordPress SEO.

I'm not actually big on updating to the latest WordPress version unless l'm convinced it's been tested awhile and plugin authors have had time to update. While there is an occasional security fix, they can easily mess up something else.

I find this plugin is worth it to me to be able to tweak themes now and then. That's my 2 cents.

Wade Watson