Jason, have you worked with WordPress before? As a plugin, this adds functionality to WordPress, but it doesn't take any away.
For your "subcategories of reviews" question, you would create WP categories. When you post about a shared host, you tick off the shared hosting category. When you post about a dedicated host, you tick off the dedicated category. Most themes, including the sample theme, show a list of categories in the sidebar, but you can put them anywhere in the theme.
About reviewing employees, make a post or a page about each employee. This plugin adds the ability to collect ratings with the comment form, and the comment form can appear on any post or page of WordPress.
Take a moment to think about what people have done with WordPress. It's not just a blogging engine, it's a full CMS. I've created dynamic content websites (
Website Goodies - Webmaster Resources, Articles and Website Tools), blogs (
Dan Grossman » Building web services one day at a time) and ecommerce sites (
WordPress Review Site Plugin » Turn WordPress Into a Powerful Review Site Engine) with WordPress. It can do all of that without extra plugins. So on top of all that, with WP Review Site, you can now turn the comment box into a review area with star ratings, display average ratings on any post or page, and sort post lists by weighted rank... plus the bonus tools.