A great album, by the way…
iTunes has has tripled the preview length on their song previews to 90-seconds. However, it seems that not all songs have the 90 second previews. Some either haven't received the update, or (perhaps) some behind-the-scenes deals haven't been worked out with the music publishers.
Other songs don't qualify: anything under two minutes and 30 seconds will continue to only offer the 30-second previews we are used to seeing with iTunes.
Still, it's a great way to get a better feel of the song.
This was talked about a while back, but the feature just began rolling out recently.