As most of you know every professional Joomla! template comes with a framework which holds the whole style, design and features. To me, if Joomla! is the body, the framework is the soul. You need a great soul to have a great character, no matter if it comes down to a person, product or whatever.
In the early days of my template development I've tested many frameworks like Warp, Gantry, T3 and Helix. My first choice back then was Warp 6, which offered very flexible (for the time...) functionality and features. After that I switched to Helix 2 and Helix 3, which are both very well built frameworks. In the mean time I was reading about Gantry 5 and all the cool stuff that RocketTheme team planned to do with it. I followed the progress and was there when they released it - not literally of course, I was at home, downloaded it and tried to play with it :)