Like you've seen everywhere else on the web, Adobe has released Adobe Reader X (10.0) with sandboxing. If you want to read the gory details, start here. Here's a direct download link.
What I'm here to tell you is how to make sure you don't lose any security when you install it.
You've got to do that again in Reader X.
Click on "Edit" and then "Preferences." Select "Trust Manager." Uncheck "Allow opening of non-PDF attachments with external applications."
Click on "Ok" and you're ready.
It sure is frustrating that Adobe didn't keep security preferences from the previous version but did keep some non-security preferences, e.g. disabling of the splash screen.
When you open your first document, you'll see this little tool tip in the upper right corner. If you hover your mouse over the top right corner of it, an "X" will appear. Click that and the tool tip seems to be gone forever. Irritating!