I'm not a fan of most seo tools. At least not the ones you download and use to tell you how to optimize your site. Most are out of date pretty fast and often even worng in their advice. I think all still tell you that you need to optimize your meta tags and quite honestly you don't even need to have them any more.
The best tool of all in seo or anything really is your own brain. The more you learn and understand how search engines work and what they like and don't like the better you'll be able to optimize your pages and site.
There are some decent tools online, but the idea is to use them to gather information about your site or competitor's sites instead of using them to tell you how to optimize your pages. I like the
Aaron Wall's tools at SEO Book and some of the tools over at
SEOmoz are pretty interesting.
Mostly though I use my own understanding and experience and check the tools the search engines themselves provide as well as the advanced operators to check things.
Tools like SEO Elite can be useful sometimes, but they won't tell you how to optimize your site. Most of the information can also be found in free online tools.