I've dropped Opera on my Macs. Its just too processor intensive on my old G4s Firefox is about 5x worse for processor usage for some reason (might be exaggerating a bit). So I've switched to Safari 4 Beta, and it is really nice except its pretty slow on opening new tabs slower than Opera or FF. But I think that is because its trying to load its fancy 'speed dial' like interface. There is probably a way to turn that off, but it hasn't bothered me enough to look into it.