Oh my God! I've been using FreeBSD for years and it has sandboxing as well! Fuck obviously they are trying to trap me in! Oh and the sky is falling, damn you Al Gore.
Sandboxing is a well known security mechanism. Apple has been weary of viruses for a few years and is being extra paranoid. Nothing like an "AppStore spreading virus LOL" story to brighten up the PR department.
If modern OS level security mechanisms scare you, install Windows 9x and be happy.
Absolutely... this is only a GOOD thing. When you install an app, you will now know that it's not doing a lot of nasty things you don't want it to. It's not just viruses either.... think Skype sneakily adding plugins to your web browsers without even asking.