The user script, which you can download and install here, modifies the avatar display in your Twitter.com timeline to include both the person you're following's avatar along with the avatar of the Twitter user they retweeted. The two avatar display makes it more clear at a glance both that the item is a retweet and which of your followers it came from.
Here's how the display appears after you install the script. It attempts to solve the issue mentioned by a number of folks who have felt that seeing an unfollowed user's avatar suddenly appear in their timeline can be somewhat jarring. Although people who primarily use clients to access Twitter won't be able to get much benefit out of this script, those that have occasion to visit the actual Twitter.com site and who might take delight in customizing the new retweet experience might find this script just the ticket.
What do you think, is the script an improvement over the default retweet display?