Media players

There are many of them.
Some feature rich, some extremely minimalist.
The major ones are Windows Media Player (WMP) and iTunes.
Both offer good functionality and a good GUI.
If you are new to computer based audio, they are a good starting point.

One might also argue that their functionality is limited.
The average user is often struggling using these applications.

Apple and Microsoft like to keep it simple as more functionality introduces more complexity than some can handle.

I tried a couple of media players.
Important for me:

• A good GUI, must be able to browse and search my collection in a flexible way. All those minimalist interfaces like browsing a file structure only, are wasted on me. I don’t have a computer to emulate a rack of CD’s.

• Cover art, the easiest way for me to recognize an album is by the cover rather than by title

• Support for the composer tag and custom tags
• Searching, often more convenient than browsing endless navigation tree's
• Audio driver support, I want bit perfect output or at least bypassing the Win mixer.
• Support for different audio formats including FLAC.

• Gapless playback. Nothing as irritating as a gap in a live concert or between two movements played as one.

Is WMP bad?

The audiophile community things so. This is not a high-end player.
As usual, you will find a lot of strong opinions and very few facts.
The negative image of Microsoft might be a major reason for the dislike of WMP.

Interface

The interface is a basic one. Functionality is sufficient but you can’t configure it.

Cover art

All cover art is down sampled to 240x240.
If you manually added images in a higher resolution, WMP12 is not your player.

File formats

Support for lossless formats is limited to WAV and WMAL.
As the tagging of WAV is rudimentary, I advise against using this format.
You can use plug-ins to play and tag FLAC but this might be at the expense of stability.
If FLAC or a wide support of other lossless formats is important to you, WMP is not the best choice.

Tagging

You can select tracks and do a manual lookup. As WMP uses AMG, the results are very good. If you are tagging classical, I do think AMG one of the best.

Streaming

Microsoft is one of the DLNA members.
My (limited) experience with DLNA and Win7/WMP12 is positive.

Sound quality

WASAPI is Microsoft’s own ASIO.
WMP only supports Direct Sound.
I do think WASAPI offers a better sound quality.
As usual with this type of claims this is valid only with my music on my gear in my room with my ears and not to mention my perception. YMMV for short.
Obvious if you do think WASAPI sounds better, WMP is not your choice.