It doesn't have any new features. Though it may be a huge technological leap underneath, Apple's mainstream user base is looking for new, flashy, cool stuff before they hand over $130.
$29 (or $10 if you bought your Mac recently) is a price that I don't see how anyone can refuse. For all the small, but subtle improvements that just makes using the OS easier, quicker, and more efficient, $29 is a downright bargain.