Its been too painful for me of late.. a good 3 minutes sometimes loading a page and also get alot msg's like "script is taking a long time.. do you want to wait" with Firefox.
Unfortunatly ive had to park alot of my domains elsewhere. Hopefully Ed can get things upto speed soon. Maybe something like eaccelerator, mod_gzip or speeding up mysql could help.
Or if you wanna spend a few quid Ed how about clustering a few servers and get a load balancer in