What are the technical merits of Block Class?

Well from recent experience working with local and multiple staging servers we have had some blocks not have the same IDs between servers. This would allow us to target theming without worrying about these sync issues.

Also I would suggest that if using a grid based theme a configurable block class allows the layout properties of the block to be taken care of by layout classes like 'span5' etc in bootstrap.

And one big advantage is the one CSS classes have in general: you can use them multiple times within the same html document.
Just create a new block, put in your desired class and voila, theming done.
Otherwise you would have to edit the css to match the new CSS ID...

Wanted to add that this is one our essential Drupal modules. It has also replaced modules that we previously attempted to use to enforce mobile or screen block display. Now we just add the class that defines whether it should be displayed based on screen size and the blocks render flawlessly. A "must have" module.

#3 really make sense.

Thank you very much, guys. Very useful.

If anyone has any question please comment okay?!

Thank you very much, people.

Regards.