I suspect your slowdown is primarily caused by slow rendering speeds rather than the database or site itself being particularly slow.
If you haven't already, try going to your profile and toggling the collapse topic preview checkbox so it doesn't show that. I changed some things around so that it only sends that info if you explicitly want it (rather than sending it to everyone and hiding it from you if you don't want it). In other words, turning that off means you get MUCH leaner pages. There's less requested from the database, and less your browser has to figure out how to render. Also, if you're not logged in, you don't get those at all.
Also, you may want to consider turning off the post preview. I've seen that seem sluggish on some machines. It catches up with you, but it can make things feel slow.
