I can now confirm (having seen it myself) that Snow Leopard 10.6.2 (upcoming update, not released yet) DOES INDEED fix the bug that caused anti-aliasing not to work in Second Life and WoW, among others. It also fixes certain performance issues and kernel panics in graphics drivers.
So... anyone waiting to upgrade to Snow Leopard, wait no more once 10.6.2 hits.. it's the real deal. I saw it and wow, what a difference!!