I must ask, why the name “Gridless”? Surely HTML/CSS frameworks and grid systems are completely different things? The name almost seems to suggest that the use of a grid is a bad thing. Just the way I perceived it :)
I checked out the demo, expecting to see some nice use of grid layouts but without the dreaded "silly classes."
But no. I see some OK-looking forms and tables in a fairly linear structure.
Indeed, true the name, it is gridless.
Do you need a framework for that?
"Beautiful typography with a vertical rhythm."
Even granting "eye of the beholder" and all that) , there's actually not much rhythm going on here.
The problem with grid systems is that they include classnames and ids which should be unique to each project. You can still use grids, but please don't use span-x classes, customize the classnames and ids to suit to your project. And doing that isn't impossible or extremely hard, there are a lot of tools out there for that: Sass/Compass, LESS, Blueprint's compress.rb script etc.