CSS template-based layouts, or something like them, have been a long time coming. John Resig has blogged about them recently, echoing the attitudes of a few people, it seems. I generally agree: this looks great, and will be a vast improvement for HTML+CSS web development: finally HTML document structure will be largely separate from visual layout. This is something that CSS grids/tables completely fail to do - divs still have to be in row>column order: a semantic change from HTML tables, and nothing more, and they still aren't supported by ie yet anyway (EDIT: Xanthir points out below that I was confused: CSS3-grid is actually a completely separate proposal to tables, and it's basically the same as what I suggest here, albeit without the ability to name the grid).
Yep, of course there are a few things I'm concerned about (and as there should be - if there weren't I'd know I hadn't been looking hard enough). First, there are a few minor points (Disclaimer: I may have missed or misunderstood parts of the spec. Feel free to correct me):