Microsoft's underappreciated Zune PC software has come a long way since its first 1.0 incarnation, a bastardized version of Windows Media Player that lacked some of its inspiration's best features. Starting with Zune 2.0 in 2007, however, something wonderful happened. The Zune PC software was rewritten from scratch and became a beautiful if incomplete media player. But most of the functional holes in 2.0 were fixed throughout the 2.5 and 3.x releases. In Zune 3.0, Microsoft fleshed out the software with Mix View, Channels, Picks, a gorgeous new Now Playing screen, and other features. Now, in version 4.0, things get even better. And the software that began as a sad also-ran is now vastly superior to its only real competition, Apple's iTunes.

Looked at generally, Zune 4.0 is another evolution of the software that began with Zune 2.0. (And seriously, let's all just pretend that the Zune 1.0 PC software never happened.) It features the same basic interface, the same basic media views, the same Zune Marketplace and Zune Social integration, and the same basic device sync, playlist, and disc burning functionality. But as with Windows 7, what Microsoft has done in Zune 4.0 is take something that was good to begin with and just make it better by rethinking the details and getting the fit and finish right. Where Zune 3.x was good or even excellent, Zune 4.0 is superior.