Looks good well done.
Minor suggestion / feedback, if you're anal like me about "white space" in sidebars ...
You can create a "postformat" that includes a dynamic sidebar, then use a single widget in that sidebar that will output something 'randomised' ... e.g. an advert or an image. Then for every post that is listed, it'll be 'full width' with a different item to the right (or left, depending where you put the 'sidebar'). Here's an exampe, in case I've not explained well: http://misc.s-t-u-f-f.net/category/some/funny/
Downside is that you'd lose the first couple of non-random widgets you currently have in your sidebar. You could get around this by putting them as a header or a footer in 'category.php', 'archive.php', 'tag.php' etc. Not sure if that's too much trouble, not an issue for you, etc., but thought I'd share!