I like the clean theme. It's clean. The more theme is still clean (after removing the background image) and allows configuring colors and as such also quite nice. But there are still three things that I find annoying: the navigation block, the administration block, and the "Add a block" block on side-pre even if I move all other blocks to side-post. So I've drafted a simple theme, derived from more. I call this theme "cleaner". It "fixes" those three things with a few simple modifications.
First, I made side-post the default region in the theme's config. IMO it creates a cleaner and more intuitive look. I had to override columns2 layout because it was hardcodedly laid out with side-pre.
Second, I set the theme to omit the administration and navigation blocks in browse mode, and show them only when editing. This required overriding the block_manager. It also required adding to the theme's core_renderer (which extends the clean's one) the header method in order to add the editing button to the front page.
One of the nicest effects of the latter is that in pages where I don't add any blocks the main region stretches all over the page. It's just cleaner that way.
That's it. If anyone is interested I can push the code to git
sooner than later.