Yoast’s WordPress SEO plugin is great. I use it on pretty much every WordPress site I deploy.
But recently it’s been getting more and more obtrusive, adding a bunch of columns to the admin screen and a ‘SEO analysis’ section to the publish meta box. Here’s a few lines you can drop into your themes
functions.php to scale it back a bit, removing the columns, admin bar menu and page analysis
For the more advanced user I’d recommend a look at the plugin API documentation.