Just need a little clarification. Snow Leopard will be released in September and will cost $29 to existing Leopard users, and $129 to Tiger users. Will the DVD be the same for these two, or will the $29 version be just a "delta" update, i.e. you can't boot from it and install from scratch? If not, how do they differentiate between Tiger and Leopard users? Also, I pre-ordered mine from the Mac OS X Up-to-Date program. Will this come with just a delta update or the entire thing? Am I making sense?