In general the site sucks for 1 of 3 reasons:
1) disks aren't fast enough / don't have enough disks (DB servers)
2) not enough CPU (web servers)
3) load balancing (the bug we fixed)
Having just fixed #3 last night, and #2 by buying a bunch more web nodes the other week, things are looking good. We also just got a new pair of DB servers, so while #1 isn't a problem yet, we're ready with new hardware.
Of course, Murphy will come and kick my ass now that I've posted that things are good, but whaddya gonna do?