Quintessential Player is a free media player for your audio and video library. It's fully skinnable and has many plugins available.
The Quintessential name has been around for many years, and this 5.0 version shows its age in both good and bad ways. As an alternative to iTunes, it doesn't have a dedicated podcast area, but its playback options are a little better. The best example of this is the play queue panel, which can be opened to create an on the fly playlist, which is great for parties.
Otherwise, while some users may like changing the appearance, this doesn't add to the functionality, which is lacking in some areas. The main problem is the equalizer. For people who like to tweak their bass Quintessential Player's equalizer will be hopeless, as it hardly effects the sound at all. The visualizations that come with it are pretty old school, and look really our of date even when compared to those in Windows Media Player.
While this 5.0 version will no doubt be updated over time, currently it seems much less stable than its established peers and is slightly buggy. It is also fairly resource hungry. If you're a fan of customization it's definitely an option, but it's hard to see an iTunes user migrating to Quintessential Player at the moment.
Quintessential Player is slightly quirky, sometimes in the wrong kind of way, but does have some interesting features