But Twenty Eleven has a serious flaw in that the sidebar is not visible on single posts, and there is no template to get around that. You need to do a major hack to both CSS and code to get right on track again, which kinda disables the advantages with the theme.
This is simply not true, I’m using Twenty Eleven for my website Future Web Blog and I literally had to add one line of PHP to the post template file. The rest was some minimal editing of CSS.
In my honest humble opinion Twenty Eleven trumps many of the bloated paid for themes out there today. I won’t go into detail why here, if you want to know my reasons see this blog post.