Installation is fairly simple. Unpack the module, and then download a couple files from the Whizzywig website. These files are whizzywig.js and then you scroll down further and follow the instructions for the sort of buttons desired on your site. Assuming you want image buttons, download buttons.zip. Make sure that whizzywig.js is downloaded to .../modules/whizzywig/whizzywig/whizzywig.js and the contents of buttons.zip are in .../modules/whizzywig/whizzywig/buttons/*.gif. Once you've set this up simply enable the module.
The Whizzywig module has its own settings page. If you have installed IMCE this module can use it for uploading images. A curious thing is they recommend disabling the HTML filter. The HTML filter is a safety requirement so that your users do not add nefarious content to the pages on your site. Apparently Whizzywig uses the full breadth of HTML and needs to support "all" tags.
The issue raised in Conflict between WYSIWYG and Line break converter apply to Whizzywig as well. This effectively prevents installing Whizzywig on a site with much content entered the traditional Drupal method.
Whizzywig has some mis-behaviors. Sometimes when hitting RETURN at the end of a paragraph it adds extra line breaks. Sometimes hitting DELETE to remove extra paragraphs doesn't do so.
There doesn't seem to be effective keystroke shortcuts for 'bold' or 'italic' or similar buttons. That is, on a Mac (which I'm using) typically one uses COMMAND-B to switch to Bold (on other systems this is CTRL-B). This didn't happen (on my Mac) for any of these. Instead switching to BOLD (or other changes) requires a) click on the button, b) click back in the textarea. When clicking on toolbar buttons the keyboard focus leaves the textarea requiring the user to click back in the textarea to type text.
I tried some color changes and this feature doesn't work very well. Changing text color does the expected change, but there is a "highlight" feature which doesn't make any apparent change.