It's not as huge a leap as Windows XP to 7 (or Vista I guess ...), but it does bring around some improvements that people are going to be excited about.

For most users no, but for $30 its kind of hard to make excuses not to upgrade.

I'm a huge fan of the ASLR and sandboxing changes so security wise there are good reasons to upgrade.

What sandbox changes did they make? Is that the app store apps can't open documents without a user selecting them in a file chooser thing?

I think that is unsigned apps require the extra dialogs/etc...

http://developer.apple.com/library/mac/#documentation/Securi...

That has the most info, i'm digging through the changes.

Yes, it is, but about 1/2 as much so? They release new versions every 2 years or so, and most people upgrade.

I feel that if you're a big user of the Mac native apps then this is well worth the $30. Fullscreen mode is a nice thing to have too. In the end, I don't think you can lose for $30.

EDIT: I'm wrong. The release is downloading. This is indeed a very big deal but I'm really surprised they haven't made more noise about it.