If you're going to call something "iTunes Preview," it'd be nice to, you know, actually be able to preview songs, and now you finally can.
To get it to work, head over to iTunes Preview through Apple's iTunes Charts page. Once there, mash on any album or artist and then hover your mouse cursor over a track number. You'll now see a little play icon which, when clicked, results in a 30-second snippet.
There are some caveats. You'll to have iTunes installed, and you can't preview an entire album. Nor does iTunes Preview offer up samples of movies, TV shows, audio books, or anything other than music. Still, it's a start, and a badly needed feature if iTunes Preview was going to live up to its name.