FV Antispam is a powerful and simple antispam plugin. It moves any spambot comments directly to trash and allows Akismet to just deal with human spam.
This way your spam folder is not overwhelmed with all the obvious spam messages. So you can look at this folder to check the spam messages detected by Akismet for example. And with new WordPress versions, you can also check the trash folder, to make sure that our plugin works correctly and only deletes what's really a spam.
Same reason as above question, if a comments is already blacklisted, you don't want to think about it in spam folder.
When you are logged in you should see a notice above each protected Filled in form. You will also see a warning in wp-admin Dashboard if there is any conflict with your Filled in forms.
Live Comment Preview works, but you have to change the textarea ID in the live-comment-preview.php file on line 124. You can find out that the ID is by looking into the source code of the page with comment form on it. It will be an unique string of seemingly random numbers and letters like "a7391152e", so use that.
jQuery Comment Preview is not so lightweight as the Live Comment Preview, but you can set the ID in options, so you don't have to edit files.
Please check your template HTML and CSS for that element. Ideally it should use standard WP comment_form function and the same kind of CSS as the default template (TwentyTen). It needs to have id="comment".
Same as above - make sure you use standard WP functions for display of comment forms. When you check out HTML source of your article page with comments bellow it, you should see two textareas - one with ID comment and the other with ID consisting of random numbers and letters. The first one should be set to invisible by this plugin.