As soon as I've read this news 20 minutes ago, I've turned on the wireless in my Kindle DX International and let it sleep as I've had my breakfast.
Now it's magically version 2.5!
I have no time to be fiddling with it now, but I've already checked out the collections (still have to find out how to display collections in alphabetic orders, right now it looks like they are only displayed the most recent first).
The web browser was limited to amazon's site in my KindleDXi, now I can browse wikipedia and a bunch of other sites. Great news for international users.
I'm already using the password lock protection
I'll check PDF features later.