I was really impressed by concrete5. It provides so many ways for its customization. It took me not so much time to convert one of my templates into concrete5 theme. The process is really simple for anyone having basic experience in web development. So the basic steps are:

1. Create a new folder in themes directory.
2. Create there a plain text file description.txt with only 2 lines: the first should have theme title, the second line contains a short description.
3. Create a ‘thumbnail.png’ file with 120×90 thumbnail for the skin.
4. Create ‘default.php’ file with the xhtml or html code of your skin. For the editable area, use the following code snippets:

$ah = new Area('Header');

Where Header is the name of current block. Very simple!

5. Upload all related files for the theme (like css stylesheet, images, etc.) in to that specific folder.

Basically it takes less than an hour to convert a single page theme. Of course it will take more if your design will be based on several page types.