Rated 5 out of 5 stars

Very neat. The only thing I didn't like was the messages didn't have alternate shading. So, I add the following in my Userchrome.css

treechildren::-moz-tree-row() {
min-height: 22px !important;
background-color: #ffffff;
}

treechildren::-moz-tree-row(odd) {
background-color: #f1f3f8;
}

/* -- override the mailbox folders list -- */
#folderTree > treechildren::-moz-tree-row() {
background-color: #e5eaf4;
}

Now its perfect! :D