I use Firefox. Running Safari on a Mac is really just about as secure as running IE on a PC. As in not very.
Firefox on a Mac is the most secure combination going (and it's also the combination for those with the
highest IQ scores too, though I doubt I qualify there.)
What I don't like about Firefox is the speed bogs down after you've been using it for awhile do to memory lag, but
supposedly that will completely improve with 3.1