I agree. One of the better implementation and customisation of the Graphene theme around.
A few things you can do to improve things further:
1. There are too many lines at the bottom of each post, making the posts listing looks cluttered. Try removing the lines and leaving just one.
.entry-footer,
.post {
border-top: none;
}
2. Clean up the paddings in the footer
#footer {
padding-top: 10px;
}
#copyright {
width: 54%;
margin-bottom: 0;
}
#developer {
width: 29%;
}