I'm only a user but here's my contribution:
* O.S requirement: Only Windows
Of course, and I don't think Steven will port it to Linux and OSX. Do you realize he should rewrite it almost from scratch?
* Features: Video playback missing and No outbound streaming
Thank god, it's a music player, not a media player.

And I don't see much use for outbound streaming.
* Audio Format ability: Perfect, except for no lossy compression for Real Audio
Frankly, who cares about Real Audio support? This (crappy) format is so 90's...
* Container Format ability: MP4 and Ogg only
I'm not sure some esoteric containers would be much use to anyone.
* Scalable, composite and emulation format abilities: NSF only
Again, few people in the world will use this.
* Protocol abilities: No RTSP and MMS
I don't use streaming, so I'll skip this point.
* Optical media ability: "?" for DVD-Audio and HDCD
DVD-A support could maybe be useful. HDCD sure would.
Now, about this wikipedia page: it's misleading, plain and simple.
* Included are lots of players whose development has been stopped for up to 10 years (Sonique, Zinf, Audion, Musicmatch Jukebox, Listen, XMMS) or some very ultra-specialized players, like Napster or MPXPlay (a console player for Windows, really?

).
* iTunes and WMP are not included because they're labelled as "video players". That's ludicrous, since they're probably the most used music players in the world. And where's Winamp? Well, it's a "video player", too.

And the same goes for JRiver MediaCenter.
* Tag support is split between two tables:
First is the "tag flexible" column in the "Extended features" table (quote: "
Flexible tagging is the ability to read or write custom tags, apart from the default ones like title, album and date. Users can use custom tags to provide additional information to media files. Custom tags work via ID3v2.4 (via the TXXX tag field), Vorbis comments and APEv2"). What about displaying, sorting and filtering them, searching for them, in
every part of the player? If it's not possible, then they're useless. Now some of these players can't do that. You can see them in a "properties" windows, and that's about all.
Second is the "Metadata ability" table. Well, I'm sorry, but if you don't support custom Vorbis tags, then your support is not "YES" but it should be labelled as "Partial". Because custom tags are part of the standard from the beginning. Splitting "tag flexible" and "Metadata ability" makes no sense.
* Devoting lots of columns to features nobody cares about is fine, but it doesn't tell you about a player's usability. Same goes for some features, like skinning. And it doesn't tell you how often the player is updated, how reactive and receptive the developper(s) is (are).
In conclusion, not much sleep to lose on this page. MusicBee is already in the top3, features-wise.

Edit: I just saw there's no mention of multivalued tags support, which is nonetheless essentiel.