Actually, Tom, I’ve been removing gridding shortcodes based upon bootstrap – like Intense – and I’ve found the unsemantic grid to be surprisingly easy and as you say very solid – I am amazed.
As for version 2.0, the site speed has been GREATLY noticeable.
I am in the process of speeding up a site for a client and when I upgraded to GP 2.0 I was surprised at the scores I was getting. I can usually get a decent increase by doing the standard stuff and combining plugin CSS and JS. But in this case, upgrading to 2.0 was really amazing – I mean it when I say great work rewriting all the Jquery and optimizing your framework. Its Fantastic ( makes me look like a hero for once ).