This is the last question I've come across requesting general tag cloud styling. Try to find other comments/threads which have similar requests and try to work them in to the plugin.
Request for justifying text: http://wordpress.org/support/topic/how-to-justify-the-tags-in-this-widget
Request for displaying as a list of tags: http://wordpress.org/support/topic/show-tags-in-list
Consider both display:list-item and <ul><li>
Another request for displaying as a list: http://wordpress.org/support/topic/plugin-ultimate-tag-cloud-widget-show-as-bulleted-list-in-alphabetical-order-instead-of-cloud
Justifying and centering done
<ul><li> seems cleaner, implemented that way now