I haven't always worked with CSS, as much of my work is involved with coding. However I love playing with CSS, and I love that in its purest sense it's so very elegant and powerful. I've always been of the philosophy that you should be able to take one basic html structure, and apply virtually any style you like to it. It's the zen CSS and it's a proven technique.
I've known about the grid system for CSS for quite some time, as there have always been templates available that use it, but I'd never really investigated in more detail as to what it actually meant. I'd made do with basic templates, and tweaked them to my liking. The grid system boils down that philosophy even more, by dividing up the standard 960 pixel width site into 60 pixel blocks. Group together those blocks in different arrangements and you have a very flexible yet easy to manage layout. Actually the 60 pixel blocks allow for 18 columns in the page. In a way it takes me back to when I started writing games way back when I was a child. I'd use graph paper to design the sprites, and block out the pixels to design a sprite for a character or an object.
It's never been a more exciting time to be in web / application development.