I used to use FireFox, but after several updates, esp. to FF4, it got to be really sluggish-- beachballing after clicking anything, typing was lagging horribly, etc. So I switched to Opera, which I'd had a good experience with before. Same story. I do have an unusually large number (for most people) of tabs open-- 70 atm-- but FF used to be able to handle 120+ tabs no problem. I don't have a ton of stuff open right now, just Opera, Word, a VNC server, iTunes iChat, Preview, and the Software Updater. Every app besides Opera runs fine. Switching Spaces is smooth, Exposé is smooth-- it's just the browser that sucks. Temps right now are 77 degrees. Quit the browser, and they drop to 62. I just don't get it.