Coming from an ignorant audience members point of view (me) in simple terms, the visual appeal is a little lacking, and the page takes a considerable amount of time to load.
The visual aspect:
I'd say include a bar graph of positive vs. negative. If you want to go even fancier, do a "growing graph," where the graph values start at the previous query's results (or zero), and "grow" (or shrink) to the new query's results. I'd also add a background, or a border, or add something to highlight the main content. But I like the logo and colors!
I mean, there are tons of great options for design/layout, and I just think it needs...something. Does that make sense? (Of course, if design doesn't matter, then it looks fine).
As for page optimization, it has everything to do with loading THAT many tweets, so I'm not sure if there's a way to fix that without direct access to Twitter's DB.
Just my opinion :o
Also, nice ascii in your source :)