If you're planning on buying it anyway, and don't plan on waiting in line at the Apple store the day it comes out, maybe you'd like to buy it at Amazon and throw us a referral? They've set up a special landing page for you to get all the details - right over here (The W at Amazon).
Keep in mind this'll only work on Intels - if you have a PowerPC, you're stuck at 10.5 (and probably need to think about upgrading some time in the next 24 months).
Mozilla just announced a security flaw a couple of days ago. They've got a patch up on their site (addons.mozilla.org). The patch (the page includes directions on how to do it manually) turns off IDN (International Domain Name)