I have tested many themes, free ones and premium ones. I've also tested some famous "framework+theme" and "framework-only" solutions.
This is my favorite. It's a framework with a nice clean default theme that lets you customize many things. It's based on Bootstrap and LESS CSS and it is perfectly responsive, with a very nice look and great functionalities.
Some reviews complain about the fact that it is not really free and you have to pay for the premium version.
I can't understand those silly complaints.
You can use a great free version of a bootstrap, drag and drop framework, with all the advantages of a frequently updated and super clean code professional framework, and if you want more features (the free version still has many), you can buy the pro version.
I like this framework so much.