With a couple of days of having looked at it, I'm still broadly happy with what I've done here, although I'll admit that I keep wondering about the color scheme, given the number of people who still find it too dark. I definitely need to rearrange and reorganize the blog, though, since there's enough content here that navigation isn't as easy as it ought to be, but that's easily done.
The bigger issue for me is figuring out how to tweak the size and padding of the columns to something slimmer yet still readable. That may not be possible, I don't know, in which case I might need to return to a single non-post column, but I'd rather not since I find three columns strangely appealing to me.
As usual, if anyone has some practical advice on better implementing any of these things, I'd be grateful, as I lack the technical skills to do many of them myself.