I didn't get to really tear into it but I gave it a quick test run. It definitely warrants closer inspection. I need to create a more complex .psd to see where it breaks down.
I didn't inspect the code other than a quick scan with firebug. From what I did see, it relies heavily on absolute positioning. There were also a number of div's with inline styling.
It does beg the question though. How bad is absolute/relative positioning vs. floating and clearing?

Personally I try to write pages that are easy on edits. They require a bit more work upfront sometimes but I'm always happy to see that I didn't paint myself into a corner. z-indexing just seemed too much like iframing to me so I've avoided it. But there are times when I think to myself, "Sh*t, I could just give this position:absolute, give it a top and a left and be done with it."
After looking at the code generated by sitegrinder, I asked myself why I don't do it more often. I didn't have an answer. So now I'm wondering, what are the inherent bad sides of static positions and sizes?