I'll have a look to see what the differences are, gzip is already enabled so it might be less than on a site that sends all the data in plaintext over the wire.
Also, you could cut down the size slightly by shrinking div names. Sure, with gzip "aside.sidebar" isn't going to take much extra space, but it will take some.
(That being said, please don't do this. Minified JS is bad enough.)
I think I'm pretty close to the 'sweet spot' where further optimizations are both a waste of time and make the result much less useful in the longer term. But just for the sake of research I'm more than willing to play around to see what happens.
In that case... I wonder if reordering things (e.g. CSS rules) could improve the compression ratio.
I'm still at the stage of dropping rules that aren't used. CSS tends to get pretty inefficient if enough people have hacked on the file and the one on my site is no exception to that. It'll still need some work. But even that is already in the realm of 'diminishing returns on investment'.