I use a variant of this, for the sole reason that it provides a reasonably flexible grid system that is very easy to use, keeps everything proportional and cons

I use a variant of this, for the sole reason that it provides a reasonably flexible grid system that is very easy to use, keeps everything proportional and consistent, and works in all modern browsers. I don't enjoy spending lots of time tweaking CSS for each site individually, when I can just throw it on a grid and have it looks great.