If you're going to switch, Firefox is the only real alternative. Chrome, Safari, and Opera are all new & sexy, but their market penetration is very low, and most web developers don't bother to support them. So while most web sites work in them, some won't, and in those cases you're going to need to have IE or Firefox as a "backup" browser anyway. Not much of a product if you have to use its alternatives 5% of the time.
Well, u have to think that firefox also had its start, while (I suppose) it had that low market penetration, and look at it now: most used brower:
http://www.youtube.com/watch?v=oSG-VVRwePc
I have a mac and use Safari, which I love. I have recently downloaded Firefox because I keep getting lines of code when pages load for chess.com and I can't create tournaments in Safari (because all I see is reams of code).
Firefox is good, but I still marginally prefer Safari. Livechess works ok in both.
IE is not a fun experience for me and never has been.
You can try Camino - Mozilla Power, Mac style: I use this when I'm in my Mac