I gave the shoutbox a 4 star rating because although it's good, it does seem to lack a couple of features that I would like.
1. it doesn't appear to fully support a transparent theme. the area which you type your shout does, but where the shout appears above is a solid color background making it stand out significantly. Even though you can change the color, it's not exactly what i'm looking for.
2. it looks great on the side, but i would like it across the center. It doesn't seem streamlined enough out of the box. below the box it uses one line of text to tell me my username (which i already know since i only allow registered users to use it). Another line of text says nothing but "message." another line to enter the text. another 2 lines for smilies (which aren't collapsable in my version 1.2 :( ), and then another line to enter the shout. All of this could fit in just one line if your shoutbox is displayed horizontally. but instead it takes up too much valuable realestate. :)
3. preferably, i'd like to see more admin features. some have been mentioned, but i'd also like to be able to ban certain user names from posting in the shoutblock - since i only allow registered users to use it, anonymous shouting is not a problem.
Overall, I do like the shoutbox, but I hope there are some improvements in the future.