I don’t know how to get rid of that last 304 status code on the blog. (Any suggestions are appreciated!) The Page Speed stuff outlines more things that can be done; I’ll get to them later, as they will involve editing my WordPress theme directly, and that’s kinda on the edge of my expertise.
I do want to point out that the wiki does not implement full-page caching. The server it was on previously was running Prefork + DSO, which should be pretty dang fast, but I could never get First Byte Times like these. Most of the difference is probably the move to PHP 5.4 from 5.2 (I think?) and the addition of opcode caching. A 400-ms first-byte time is incredible to me, when you consider PHP is getting invoked for every single page view.
So yeah, I’m proud of myself now, and thinking maybe I should set up a faux-CDN since I’ve now got two servers at my disposal. 😉